THE RELATIONSHIP BETWEEN STANDING POSTURE, FUNCTIONAL HIP RANGE OF MOTION, AND POSTURAL CONTROL IN FEMALE COLLEGIATE
VOLLEYBALL PLAYERS
THESIS
A THESIS Submitted to the Faculty of the School of Graduate Studies
and Research of California University of Pennsylvania in partial fulfillment of the requirements for the degree of
Master of Science
BY
CATHERINE L. DOUGHERTY
Research Adviser, Dr. Rebecca A. Hess
California, Pennsylvania
2005
ii
iii
Acknowledgements
Firstly, I want to thank God for waking me up this morning, for granting me the grace and perseverance with which I could accomplish this prestigious achievement. If it were not for the ability he has bestowed upon me, both mentally and physically, this feat may not have been possible.
Thanks to my parents, Bob and Judy Dougherty, for the many sacrifices they have made in order for me to obtain such a dignified education. Their constant encouragement, reassurance, and devotion have promoted the diligence necessary to complete this degree of success. Thank you, also, for instilling in me the firm, Catholic belief that God will provide for me and protect me on my journey through life. I will offer up all my accomplishments, tribulations, and defeats to gain his grace.
Thank you to my committee, Dr. Hess, Dr. Reuter, and Jeff Hatton, for the professional advice and the determination to make this endeavor a hopeful success. You have proven that nothing is merely handed to the undeserved; but with the proper amount of persistence (and loss of sleep), even the worst of researchers can develop a fundamental competence for the researching, and re-researching, process. I assure you that if I had commenced this program at the intended time, this would have been done two months ago. Instead it seems I have learned the necessary material after-the-fact.
Thanks to my fabulous boyfriend, Dave, who helped me maintain composure when this thesis-writing procedure had me at my whit’s end. If it were not for him, I would probably be bald in the loony-bin right now. Thank you to my classmates for the stress-relieving nights at Lagerhead’s and the many memories. Thank you to my Aunt JoAnne and Uncle Will for donating me a ’94 Acura Integra with 220,000 miles to get me to school daily. It still runs like a dream! And lastly, thanks to Lisa and Amber for allowing me to shack-up in their spare room on my air mattress to save me the excess mileage on my car and un-necessary sleep-deprivation.
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TABLE OF CONTENTS
Page SIGNATURE PAGE . . . . . . . . . . . . . . . . ii
ACKNOWLEDGEMENTS . . . . . . . . . . . . . . . iii
TABLE OF CONTENTS . . . . . . . . . . . . . . . iv
LIST OF TABLES . . . . . . . . . . . . . . . . vii
INTRODUCTION . . . . . . . . . . . . . . . . . 1
METHODS . . . . . . . . . . . . . . . . . . 11
Research Design. . . . . . . . . . . . . . . 11
Subjects. . . . . . . . . . . . . . . . . . . 12
Preliminary Research. . . . . . . . . . . 13
Instrumentation. . . . . . . . . . . . . . . 13
Static Postural and Flexibility Assessment . . 14
Dynamic and Functional Assessment. . . . . . 16
Procedures . . . . . . . . . . . . . . . . . 18
Hypotheses . . . . . . . . . . . . . . . . 23
Data Analysis . . . . . . . . . . . . . . . 23
RESULTS . . . . . . . . . . . . . . . . . . . 25
Demographic Data . . . . . . . . . . . . . . 25
Hypotheses Testing . . . . . . . . . . . . . 25
Additional Findings . . . . . . . . . . . . . 32
DISCUSSION . . . . . . . . . . . . . . . . . 37
Discussion of Results . . . . . . . . . . . . 37
Conclusions . . . . . . . . . . . . . . . . 43
v
Recommendations . . . . . . . . . . . . . . . . 44
REFERENCES . . . . . . . . . . . . . . . . . 46
APPENDICES . . . . . . . . . . . . . . . . . 49
A. Review of the Literature . . . . . . . . . . . . 49
Introduction. . . . . . . . . . . . . 50
Core Stability. . . . . . . . . . . . . . . 52
Composition of the Core. . . . . . . . . . 52
Importance of Core Strengthening . . . . . . 54
Assessment of Core Strength and Stability. . . 55
Testing for Core Stability. . . . . . .56
Testing for Core Power. . . . . . . . 57
Strengthening strategies. . . . . . . . . 58
Postural Deviations. . . . . . . . . . . . 62
Functional Range of Motion in Lower Extremity. . 66
Knee Injuries in Female Athletes. . . . . . . 69
ACL Injury. . . . . . . . . . . . . . . 70
Patellar Maltracking and Subluxation. . . . . 76
Patellar Tendonitis. . . . . . . . . . . 77
Summary. . . . . . . . . . . . . . .78
B. The Problem. . . . . . . . . . . . . . . . . 80
Statement of the Problem . . . . . . . . . . 81
Definition of Terms . . . . . . . . . . . . 81
Basic Assumptions . . . . . . . . . . . . . 84
Limitation of the Study . . . . . . . . . . 84
vi
Significance of the Study. . . . . . . . . . 85
C. Additional Methods. . . . . . . . . . . . . . 86
Informed Consent (C1). . . . . . . . . . . . 87
Institutional Review Board (C2). . . . . . . . 90
General Demographic Information (C3). . . . . . 95
Evaluation Form (C4). . . . . . . . . . . . 97
Active Hip Range of Motion Measurements (C5). . 100
Overhead Squat Assessment (C6). . . . . . . .102
REFERENCES . . . . . . . . . . . . . . . . . 104
ABSTRACT . . . . . . . . . . . . . . . . . . 108
vii
LIST OF TABLES
Table Title Page
1 Q-angle Compared to Standing Posture, 28 Overhead Squat, and Jump Recovery
2 Active Hip ROM Compared to Standing Posture, 30 Overhead Squat, and Jump Recovery
3 Knee Pathology Compared to Standing Posture, 34 Overhead Squat, and Jump Recovery
4 Vertical Jump Heights for 10 Division II 36 Female Volleyball Athletes
1
INTRODUCTION
The prevalence of knee injuries is a serious problem
for athletic trainers, particularly those working with
female athletes. Knee injuries have been traced back to
defects such as lack of core strength, postural deficits,
increased Q-angle, tibial valgus, subtalar pronation, and
associated imbalances in flexibility and functional range
of motion.1,2 While core stability and postural control are
necessary components of every athlete’s training regimen,
the beneficial effects on power and function have often
been ignored.2 If more athletic trainers and coaches were
aware of their role in optimal performance, core stability
and postural control might be incorporated more readily
into every athlete’s conditioning program, potentially
lessening the stress and workload of certain avoidable
overuse injuries.
The core supplies the entire kinetic chain with
neuromuscular control and efficiency.2 Core muscle groups,
namely the lumbar extensors, abdominals (rectus abdominis,
external and internal obliques, and transverses abdominis),
and hip musculature (psoas, gluteus medius and maximus, and
hamstrings), create stabilization and force-couple
relationships that normal function is dependent upon. When
2
normal length-tension relationships are established, the
body is provided with an environment that will allow
optimal arthrokinematics during functional kinetic chain
movements.2
Overuse injuries, such as medial tibial stress
syndrome and tendonitis, are often caused by abnormal
biomechanics of the lower extremity.3,4 While we as
clinicians may feel more informed about the effect that
lower extremity biomechanics can have on pathologies
ranging from the foot to the hip, it is also important to
consider the effect of lower extremity biomechanics on the
pelvis and lumbar spine. Abnormal biomechanics, beginning
as low as the subtalar joint, may cause compensatory
movements that lead to pathology of the pelvis and lumbar
spine. Resulting imbalances of the hip and/or lower
extremity musculature may contribute to the onset of low
back pain.3 Therefore, a comprehensive evaluation for low
back pain should include assessment of the lower extremity
for such abnormalities.3
Overuse injuries develop when repetitive stress to
bone and musculotendinous structures damages tissue at a
greater rate than that at which the body can repair
itself.5 A combination of extrinsic factors, such as
training errors and environmental factors, and intrinsic
3
or anatomical factors, such as bony alignment of the
extremities, flexibility deficits, and ligamentous
laxity, predispose athletes to develop overuse injuries.
Malalignment of the lower extremity, including excessive
femoral anteversion, increased Q angle, tibial vara
(internal rotation of tibia), genu varum or valgum (“bow-
legged” or “knock-kneed”, respectively), subtalar varus
and pronation (flattening of the medial longitudinal
arch) are frequently cited as predisposing to knee
extensor mechanism overuse injuries, namely tendonitis.5
These and other forms of malalignment have also been
implicated in iliotibial band syndrome, medial tibial
stress syndrome, lower extremity stress fractures and
plantar fasciitis.5
The kinetic chain works synergistically to produce
force concentrically, reduce force eccentrically, and
dynamically stabilize against abnormal forces. When
functionally efficient, each component of the core
disperses weight, absorbs force, and transfers ground
reaction forces. Core strength is also mandatory,
specifically in lower extremity dominant sports, to
provide proximal stability during competition.2,6 If the
distal musculature is strong but the core is weak, there
will not be enough force created to produce or control
4
efficient movements. Again, a weak core is a typical
cause of inefficient movements that could lead to
injury.2,6
Neuromuscular efficiency is promoted by the
appropriate combination of postural alignment (static and
dynamic) and stability, which allows the body to absorb
momentum at the correct joint, in the correct plane, and at
the correct time.3 As this efficiency decreases, so does the
body’s ability to react accordingly to abnormal forces.
This could potentially lead to compensation and
substitution patterns, as well as poor posture during
functional activities.3,5 Pathology of structures within the
neuromusculoskeletal system can result from skeletal
malalignment, which has been defined as either abnormal
joint alignment or deformity within a bone. Pathology can
also result from correlated or compensatory motions or
postures, which may accompany skeletal malalignment.3,4
Consequently, mechanical stress is placed on the static
(ligaments and bones) and dynamic (muscles and tendons)
tissues causing repetitive microtrauma, incorrect
mechanics, and injury.5 Sometimes this overloading of joints
and small muscles is due to the core not sufficiently
contributing to the effort. Therefore, stability and
movement are critically dependent on the coordination of
5
all the muscles surrounding the lumbo-pelvic hip complex.3
It is imperative to link common lower limb skeletal
malalignments to their correlated and compensatory motions
and postures.3,4
Unfortunately, lower extremity malalignment is less
amenable to intervention since it is congenital.
Orthotics are often prescribed to improve lower extremity
alignment. However, studies have not shown that orthotics
have any effect on knee alignment and, while they can
alter subtalar joint alignment, the clinical benefit of
this remains unclear.5 Awareness of anatomical factors
that may predispose athletes to overuse injuries allows
the athletic trainer to develop individual rehabilitation
programs designed to decrease the risk of overuse injury.
In addition, the clinician can advise the athlete on the
importance of avoiding extrinsic factors that may result
in overuse injury.5
Muscle inflexibility also predisposes athletes to the
development of a variety of overuse injuries.5 Flexibility
deficits may be improved by an appropriate stretching
program. Range of motion throughout the entire lower
extremity must be within normal limits to ensure standard
length-tension relationships and ultimately produce regular
arthrokinematics.5 If one muscle, or group of muscles, is
6
incapable of proper lengthening, it can create imbalances
throughout the entire kinetic chain. Without normal length-
tension relationships, an athlete is more prone to injury
due to improper passive lengthening and faulty eccentric
contraction of the musculature to absorb the force.5 These
imbalances and functional adaptations need to be corrected
to avoid problematic situations for the athlete,
particularly the female athlete, that may be predisposed to
such situations, as well as for the athletic trainer, whose
role is to treat and rehabilitate athletes’ injuries, if
not prevent them altogether.
Female participation in athletics has increased
dramatically over the last decade. Accompanying the
increase in sports participation is the increase incidence
of injury.7 Anterior cruciate ligament (ACL) sprains and
tears, patellar tendonitis, and subluxing patella are just
a few of the typical knee injuries seen regularly in the
jumping, female athletic population. Many of these
occurrences are due to valgus motion of the knee during
jump recovery as a result of muscular imbalances.7,8
Women appear to suffer four to eight times the number
of ACL injuries for the same sports as men.9 A greater Q-
angle (normal for females is ~ 180), anterior pelvic tilt,
anteverted hips, genu valgum, genu recurvatum, and subtalar
7
pronation are some of the anatomical differences that may
predispose a female to knee injury.7 Education about proper
dynamic stabilization of the muscles acting on the knee, as
well as hip joint, is vital.
Both intrinsic and extrinsic factors have been
proposed to contribute to the greater knee injury rate in
female athletes compared with their male counterparts.10,11
Specifically, intrinsic factors refer to lower extremity
skeletal malalignments, including excessive Q-angle, genu
valgum, femoral anteversion, and general joint laxity.
However, most of the skeletal variations between males and
females develop only after the rapid growth associated with
puberty. Not surprisingly then, post-pubescent females
suffer the highest rate of lower-limb injury when compared
with both the prepubescent female and male athletes.10-12
Some of the extrinsic factors associated with ACL
injury include motor control strategies, coordination of
movement patterns, the level of conditioning and muscular
strength, and possibly even menstrual factors affecting
ligamentous laxity.13 Only recently have extrinsic factors,
such as jumping and landing strategies, related to ACL
injuries been studied.13 Most of this research has focused
on kinetics, neuromuscular activity, and kinematics in the
sagittal plane without regard to maturation and frontal
8
plane motion. The kinematics of high-risk landing patterns
have been identified and many components of these parallel
the variations in female structural alignment with altered
motion occurring in the frontal plane.10,12 Recent research
in college-aged participants identified gender differences
in lower extremity kinematics and kinetics during landing
activities, indicating that female athletes may possess
altered motor control strategies that result in knee
positions in which an ACL injury may occur.10,13 However,
there is a scarcity of information on the landing control
strategies in young pre-adolescent female sport
participants. Perhaps the reduced injury rate in this
population is a result of using landing strategies that are
“safer” than older female participants. Conversely, these
older female athletes may be utilizing landing strategies
that become injurious when changes in the skeletal
architecture are influenced by the onset of
menstruation.10,13,14
The menstrual cycle may be one of the leading
explanations for differences between males and females with
regards to lower extremity injuries.9,14,15 The basis for this
cycle is the endocrine coordination between the
hypothalamus, the pituitary gland, and the ovaries. The
coordination among these centers occurs through the
9
circulatory system via hormones. During the course of this
cycle, the absolute levels of estrogen, progesterone, and
relaxin (thought to drastically diminish collagen tension),
and the ratio of these hormone concentrations, change over
the mean cycle duration of 28 days.9,14 This could entail a
difference in joint stability due to an increase in
ligamentous laxity.
In summary, biomechanical interaction of the entire
lower extremity, as well as the core, may be important
contributors to the risk of knee injury. Understanding the
interaction between trunk motion and those of the lower
limb joints during functional activity may provide further
insight into the resultant injury mechanism.16 For instance,
trunk accelerations at contact will have a significant
impact on coupled hip and knee flexion, and more than
likely, on alternative planar loading at the knee joint.
Thus, the lumbo-pelvic-hip complex, as well as the knee
stabilizers, must have efficient functioning to withstand
these multi-planar impacts.16 The athletic trainer is
responsible for recognizing muscular imbalances to ensure
optimal performance and possible prevention of injuries
altogether.
The purpose of this study was to evaluate the
relationship between a female jumping athlete’s tri-planar
10
active hip range of motion, and static, dynamic, and
functional postural control of the knee and ankle. The
following research questions were addressed:
(1) Does an increased Q-angle past the normal average value
(180 for females) coincide and negatively correlate with
tibial valgus and subtalar pronation in static standing
posture, as well as lead to the same observed dynamic and
functional postural discrepancies?
(2) Do discrepancies in hip active range of motion,
specifically decreased hip abduction, extension, and/or
external rotation, and increased hip adduction, flexion,
and/or internal rotation, result in tibial valgus and
subtalar pronation, as well as lead to the same observed
dynamic and functional postural discrepancies?
11
METHODS
The following sections will be addressed in the methods:
(1) Research Design, (2) Subjects, (3) Preliminary Research,
(4) Instrumentation, (5) Procedures, (6) Hypotheses, and
(7) Data Analysis.
Research Design
A descriptive correlational design was used for this
study. The independent variables were Q-angle reported in
degrees, presence of tibial valgus in standing posture,
presence of subtalar pronation in standing posture, and
active hip range of motion (AROM reported in degrees) in
all three planes.17,18 The dependent variables were measures
of core stability and neuromuscular efficiency as measured
by performance of the Overhead Squat according to the
National Academy of Sports Medicine (NASM)19, and functional
ability as measured by performance of a simulated jump
recovery. Standing tibial valgus and subtalar pronation
served as static measures, the Overhead Squat as a dynamic
measure, and jump recovery as a functional measure for
subjects’ postural control. The group used for testing was
comprised of volunteer female volleyball athletes from
California University of Pennsylvania, with and without a
12
history of lower extremity injuries. Results were limited
to those female athletes participating in collegiate
volleyball at the Division II level. The descriptive
design was useful in examining the relationship between hip
AROM and static, dynamic, and functional posture in the
female collegiate jumping athlete, which could potentially
serve as a diagnostic profile for possible injury.
Subjects
Ten (N = 10) female volunteers from the California
University of Pennsylvania’s Volleyball team completed this
study. The subjects were a mixture of uninjured and
chronically injured athletes; however, the athletes must
have been actively participating in spring training in
order to participate. Subjects were asked to volunteer
without any coercion from the coach. Data collection was
performed May 2005 (post-season). Each subject was tested
individually in one testing session. Informed consent
(Appendix C1) was obtained from each volunteer, and the
project was presented to the Institutional Review Board
(Appendix C2) prior to data collection.
13
Preliminary Research
The researcher collected results of the lower
extremity postural assessment (Q-angle measurements and
presence of tibial valgus and/or subtalar pronation), hip
flexibility assessment, and the performance of Overhead
Squat and jump recovery from three female test subjects.
This pilot work was performed to familiarize the researcher
with performance of the tests and procedures, and provide a
more accurate time frame for subjects’ participation. No
changes were made as a result of this preliminary
investigation.
Instrumentation
The following instruments were used to collect data
for the study: a demographic information form, scale, tape
measure, evaluation forms (documenting Q-angle
measurements, hip AROM, and results of static, dynamic, and
functional assessments), hip range of motion assessment,17
foot posture and tibiofemoral alignment observation,
universal goniometer, NASM Overhead Squat assessment,19 and
video camera.
14
General demographic information (Appendix C3)
documenting the age, recorded height and weight, history of
knee injury, menstrual patterns, and first day of the last
menstruation for each subject was recorded by the
researcher. The subjects’ weight was measured on a scale
(Detecto, Cardinal Scale Manufacturing Co., Webb City, MO),
and subjects’ height was measured with a tape measure
affixed to the wall at the appropriate height.
Static Postural and Flexibility Assessments
Subjects’ Q-angle was measured with a universal
goniometer and recorded in degrees by using the angle from
the anterior superior iliac spine (ASIS) through the
midpoint of the patella and to the tibial tuberosity.8 The
researcher then analyzed and compared the measurements with
normal values according to Starkey (>180 is considered
excessive for females).8 The goniometer is a protractor-like
instrument that measures range of motion of articulations
in degrees. Investigators have found good inter-tester
reliability (r = .91) and validity for the goniometer as an
instrument to efficiently measure joint angles.17
Flexibility of the hip was also measured with a
universal goniometer and recorded in degrees on the eval-
uation form (Appendix C4). All goniometric measurements
15
were taken actively (AROM) to assess the participants’
functional ranges of motion. These measurements were
recorded in degrees as differences from the normal values
documented by Kendall, et al, and Roach and Miles (Appendix
C5) to further validate postural dysfunctions.18,20 The
following ranges were analyzed: hip flexion (supine with
measuring knee flexed, other leg flat on table, pelvis
neutral), hip extension (prone with both knees extended),
hip abduction/ adduction (supine with both knees extended),
and hip internal/external rotation (seated with hips and
knees flexed at 900).17,21,22
Dysfunction in the tibiofemoral joint and subtalar
joint typically stems from hip ROM discrepancies.5 Lower-
crossed syndrome (anteriorly tilted pelvis with associated
increased lumbar lordosis), and pronation-distortion
syndrome (flattened arches with pronated feet) are common
postural deviations that may occur as a result of these ROM
discrepancies.5 Muscular imbalances found in these
deviations, such as tight hip flexors, adductors, erector
spinae, peroneals, and gastrocnemius muscles, and weakened
gluteus maximus and medius, abdominals, and anterior and
posterior tibialis muscles, are the source of faulty static
posture, and furthermore, faulty dynamic and functional
16
mechanics that may potentially lead to preventable
injuries.5
The subjects’ standing posture was then evaluated for
the static anomalies of tibial valgus and subtalar
pronation and compared with normal posture as dictated by
Starkey.8 A check was placed on the evaluation form in the
appropriate box to indicate presence of valgus or
pronation. The subjects were then requested to perform the
NASM Overhead Squat test19 with minimal instruction and the
jump recovery test.
Dynamic and Functional Assessments
The Overhead Squat assessment was observed closely for
dynamic compensations, specifically at the feet/ankles
(pronation, externally rotated feet), knees (alignment of
knee-to-toe), and lumbo-pelvic-hip complex (weight
shifting). Score sheets from the NASM manual (Appendix
C6)19 were used to rate the subjects’ performance based on
these observations, and compared to static/postural
flexibility assessments. Reliability and validity of the
NASM Overhead Squat assessment is still undergoing review
and analysis. The assessment is currently used as a
comparative tool. A check was placed on the evaluation
form in the appropriate box to indicate presence of valgus
17
or pronation. Performance was video-taped by a graduate
athletic training student for optimal analysis at a later
time.
To efficiently assess the athletes’ functional jump
recovery, a vertical jump test was administered employing
the VertecTM (Questtek Corp, Northridge, CA), a device with
colored plastic swivel vanes that displace as the athlete
jumps and hits them at their maximum height. The VertecTM
measures vertical jump heights from 6- to 12ft, and each
vane is ½ inch apart. The reliability of the VertecTM
vertical jump test has been reported to be quite high (r =
.93).23 According to the manufacturer’s suggested
measurement instructions, the bottom vane of the VertecTM
was placed at the athlete’s standing reach height (single
arm).24 The subject was then asked to jump as high as
possible and displace the vanes at the maximum height. The
athlete was allowed to squat as low as desired, but no
initial step is permitted, and the athlete must land on
both legs simultaneously. The jump height was then
measured in inches by counting the number of vanes
displaced between the athlete’s standing reach height and
jumping reach height and dividing by two (each is ½ inch
apart). This measure was then converted into centimeters.
18
To adequately examine the athletes’ mechanics upon
landing, the athlete was asked to perform three trials with
maximal effort and displace the vane at the maximal height.
One warm-up jump and three actual jumps for maximum height
were permitted for each individual with 30 second rest
intervals between each jump.24,25 Again, the jump recovery
was video-taped for proper analysis and resultant
functional compensations of tibial valgus and subtalar
pronation were thoroughly checked and recorded on the
evaluation form (Appendix C4). If the position of the
knees upon landing was viewed to be fully extended, a “/”
was also recorded in the appropriate column of the
evaluation form.
Procedures
Institutional Review Board (IRB) approval, subject
selection, and preliminary research were done prior to data
collection. A graduate athletic training student’s
assistance was also sought, and he was informed of the
intent and correct procedures for the study. The
researcher then approached the Volleyball team as a group,
explained the requirements and benefits of participation in
the study, and asked for volunteers. Thereafter, the
19
subjects were asked to complete the consent form and were
assigned a subject number with which to preserve subject
confidentiality.
The subjects’ general demographic information was
requested from the subject and documented by the
researcher. The researcher then obtained the athletes’
weight on a scale. The subjects were then advised to warm-
up on the Life FitnessTM 9500 HR stationary bicycle for five
minutes (level 5, approximately 90 RPM, seat height set to
point at which extended knee has approximately 50 of
flexion) to promote tissue warming25 and to prepare for
flexibility testing, performance of the Overhead Squat, and
simulated jump recovery. Next, the subject was asked to
remove their shoes and instructed to lie supine on the
table to allow for their Q-angle to be measured and
recorded on the evaluation form. The goniometer axis was
placed in the center of the patella, with the stationary
arm aligned with the ASIS and movement arm aligned with the
tibial tuberosity.
Each participant’s hip AROM was then measured with a
goniometer and was recorded in degrees on the evaluation
form. The subject was positioned accordingly and asked to
actively move her leg into the desired range to be measured
while the researcher palpated the corresponding anterior
20
superior iliac spine (ASIS) to ensure that neutral pelvis
was sustained. A trial movement was permitted to determine
if the motion can occur pain-free. The second AROM was
measured and recorded when the subject could no longer move
within the desired proper position of neutral pelvis.
Hip flexion was measured with the subject lying supine with
measuring knee flexed, other leg flat on table, pelvis
neutral; and hip extension was measured with the subject
lying prone with both knees extended. The goniometer’s
stationary arm was in line with the trunk, axis at greater
trochanter, and movement arm in line with the longitudinal
axis of the femur for both the flexion and extension
measurements. Hip abduction and adduction was measured
with the subject lying supine with both knees extended.
The goniometer’s stationary arm was positioned horizontally
at ASIS level, axis at ipsilateral ASIS, and movement arm
in line with the longitudinal axis of the femur. Hip
internal- and external rotation was measured with the
subject seated with knees flexed at 900.17,21 The
goniometer’s stationary arm was positioned perpendicular to
the floor, axis at the patella, and movement arm in line
with the longitudinal axis of the tibia.17,21
The subjects’ standing posture was then evaluated for
static anomalies of tibial valgus and subtalar pronation
21
and documented on the evaluation forms. To efficiently
produce the subjects’ normal stance, they were asked to
walk forward four steps and stand comfortably while the
observed postures were recorded as tibial valgus and/or
subtalar pronation.
Next, the subjects were asked to perform the Overhead
Squat19 and simulated jump recovery to observe for dynamic
and/or functional compensations, respectively. For the
Overhead Squat, the researcher minimally instructed the
athlete by saying, “Perform your normal squat with arms
overhead,” and then recorded the postural deviations, if
any. A properly-executed squat is performed when all of
the following criteria are met: feet maintained in a
neutral position (no pronation or “toeing out”), knees
maintained in a neutral position (no valgus or varus
motion), weight distributed evenly throughout the motion,
core stabilization performed to prevent abdominal
protrusion and/or low back rounding/protrusion, scapulo-
thoracic stabilization to prevent scapular protraction, and
head maintained in a neutral position (not forward).19 The
athlete was permitted one trial squat and the second squat
was analyzed, recorded, and video-taped from the sagittal
view.
22
For the jump recovery, the athlete was instructed to
reach as high as possible while merely standing at the base
of the Vertec. The lowest vane was then positioned at this
maximum standing reach height. The athlete was instructed
to jump as high as possible, squatting as much as necessary
and without taking any step, to displace the vanes at their
maximum height reached with an extended arm, and land on
both legs simultaneously. The athlete was then permitted
one practice jump. Three actual jumps were then performed
at maximal effort, and the athlete was asked to displace
the vanes at the maximal height reached. Jump heights were
recorded in inches and later converted to centimeters.
Thirty seconds recovery time was permitted to the
participants between each jump. Resultant bilateral tibial
valgus and/or subtalar pronation, in addition to fully
extended knees during the landing phase of the assessment
were documented on the evaluation forms. Both the Overhead
Squat and the jump recovery were video-taped from a sitting
position, in the sagittal plane, approximately 10ft away
for later analysis.
23
Hypotheses
The following hypotheses were considered:
1) An increased Q-angle past the normal average value
will coincide and negatively correlate with tibial valgus
and subtalar pronation in static standing posture, and will
lead to the same observed dynamic and functional postural
discrepancies (tibial valgus and subtalar pronation, as
measured by the Overhead Squat and jump recovery).
2) Discrepancies in hip active range of motion,
specifically decreased hip abduction, extension, and/or
external rotation, and increased hip adduction, flexion,
and/or internal rotation past the normal values, will
result in tibial valgus and subtalar pronation, and will
lead to the same observed dynamic and functional postural
discrepancies (tibial valgus and subtalar pronation, as
measured by the Overhead Squat and jump recovery).
Data Analysis
Data from the evaluation form was descriptively
analyzed to determine the relationship between hip AROM,
and static, dynamic, and functional postural discrepancies
24
whereby trends in static standing posture should produce
similar results in dynamic and functional assessments, and
result in a potential profile for the jumping female
athlete. A Pearson Product Moment Correlation was also
used to determine the relationship between Q-angle (in
degrees), tibial valgus, and subtalar pronation (“present”
= 1, “not present” = 2). Statistical analysis using SPSS
version 12.0 (SPSS Inc., Chicago, IL) with an alpha level
set a priori at < 0.05 was used for the correlation.
25
RESULTS
The following section encompasses the information
obtained through the collection and analysis of the
demographic data, Q-angle and active hip range of motion
measurements, standing posture, and performance of the
Overhead Squat and jump recovery. The results have been
divided into the subsequent sections: (1) Demographic Data,
(2) Hypothesis Testing, and (3) Additional Findings.
Demographic Data
Ten female Collegiate Division II Volleyball players
completed the study. The average age of the sample was 20
years (SD = 0.88yrs), the average height was recorded at
174.24cm (SD = 5.61cm), and the average weight was recorded
at 74.57kg (SD = 11.07kg).
Hypothesis Testing
The following hypotheses were investigated for this
study:
Hypothesis 1: An increased Q-angle past the normal average
value will coincide and negatively correlate with tibial
26
valgus and subtalar pronation in static standing posture,
and will lead to the same observed dynamic and functional
postural discrepancies (tibial valgus and subtalar
pronation, as measured by the Overhead Squat and jump
recovery).
Conclusion: As illustrated in Table 1, one of the ten
athletes (10%), Subject 07, exhibited a Q-angle greater
than the normal value of 180. This athlete, furthermore,
was the only subject to exhibit the traits of tibial valgus
and subtalar pronation during all of the assessments of
standing posture, Overhead Squat, and jump recovery in
support of the hypothesis.
Subject 05 had a Q-angle of only 90 (half of the
average measurement), and still presented with tibial
valgus and subtalar pronation in all assessments with the
exception of standing posture. Subject 10, on the other
hand, with the smallest Q-angle of 50, presented tibial
valgus in her standing posture, as well as jump recovery,
but did not exhibit the characteristic in the Overhead
Squat. No other discrepancies were reported.
A Pearson correlation coefficient was calculated to
determine the relationship between standing posture and
performance of the Overhead Squat and jump recovery. A
27
perfect positive correlation was found when comparing the
presence of subtalar pronation during standing posture and
the Overhead Squat (r(9) = 1.00, P = 0.01), indicating a
perfect linear relationship between the two variables.
Subjects with subtalar pronation in standard standing
posture will exhibit subtalar pronation during the
performance of the Overhead Squat. No other correlations
were significant.
28
Table 1. Q-angle Compared to Standing Posture, Overhead Squat, and Jump Recovery
Posture OH Squat Jump Recov
Subj# Q-angle
Valgus Prona tion
Valgus Prona tion
Valgus Prona tion
1. X2. X01 -7
X X
3. X1. X X2. X X02 -6 X 3. X X1. X X2. 03 -11 3. X X1. X 2. X 04 -6 X 3. X 1. 2. X X05 -9 X X X 3. 1. X X2. X X06 -4 X 3. X X1. X X2. X X*07 +2 X X X X 3. X X1. X X2. X X08 -6 3. X X1. X X2. X X09 -5 X X 3. X X1. X X2. X X10 -13 X
3. ____________________________________________ An X indicates presence of the trait during the assessment. Q-angle measurements are noted as deviations from the average value of 180. *Subject 07 exhibited a Q-angle greater than this value, and tibial valgus and pronation was noted throughout all of her assessments.
29
Hypothesis 2: Discrepancies in hip active range of motion,
specifically decreased hip abduction, extension, and/or
external rotation, and increased hip adduction, flexion,
and/or internal rotation past the normal values, will
result in tibial valgus and subtalar pronation, and will
lead to the same observed dynamic and functional postural
discrepancies (tibial valgus and subtalar pronation, as
measured by the Overhead Squat and jump recovery).
Conclusion: As illustrated in Table 2, none of the subjects
exhibited all of the anticipated deviations in active hip
ROM simultaneously, namely decreased abduction, extension,
and external rotation, and increased adduction, flexion,
and internal rotation. Therefore, Hypothesis 2 was not
supported as the hip ROM measurements could not be
correlated with the subjects’ standing posture nor
performance of the Overhead Squat or jump recovery.
30
Table 2. Active Hip ROM Compared to Standing Posture, Overhead Squat, and JumpRecovery
Posture OH Squat Jump Recov
Sub# Flex Ext Abd Add IR ER Valg Pron Valg Pron Valg Pron1. X2. X*01 -3 -1 +4 +24 +3 -1 X X3. X1. X X2. X X02 -32 -8 0 +11 -4 -7 X3. X X1. X X2.*†03 -20 -1 -8 +9 +6 -13. X X1. X2. X04 -11 -5 -13 +4 -1 +21 X3. X1.2. X X*05 -10 -3 +1 +5 +2 +1 X X X3.1. X X2. X X†06 -7 -10 -12 +16 -1 -2 X3. X X1. X X2. X X07 -8 -10 -5 +5 -3 0 X X X X3. X X
31
Sub# Flex Ext Abd Add IR ER Valg Pron Valg Pron Valg Pron1. X X2. X X†08 -16 -13 -2 +6 -1 -53. X X1. X X2. X X*†09 -18 -12 -10 +13 +5 -6 X X3. X X1. X X2. X X10 -41 -17 +1 +8 -11 -16 X3.
_______________________________________________________________Flex indicates hip flexion supine with knee bent and neutral pelvis (Avg. 1220)Ext indicates hip extension prone with knee extended (Avg. 220)Abd indicates hip abduction supine (Avg. 440)Add indicates hip adduction supine (Avg. 100)IR indicates hip internal rotation seated with knee bent to 900 (Avg. 330)ER indicates hip external rotation seated with knee bent to 900 (Avg. 340)Valg indicates tibial valgusPron indicates subtalar pronation
None of the subjects exhibited the proposed patterns of hip range of motion: ↓ abd,ext, and ER, ↑ add, flex, and IR. Therefore, the hip ROM measurements cannot becorrelated with the subjects’ standing posture, performance of the Overhead Squat,or jump recovery. Hypothesis 2 was not supported.*Subjects 01, 03, 05, & 09, showed increased hip IR and add, while †Subjects 03, 06,08, & 09 showed decreased hip ER and abd.Subjects 03 and 09 exhibited all assumptions but increased hip flexion.
32
Additional Findings
Following the testing of the hypotheses, the data was
analyzed for any further findings. Upon analysis of Table
3, all ten of the subjects (100%) exhibited tibial valgus
and/or subtalar pronation during jump recovery. Only one
of the ten (10%), Subject 01, did not demonstrate tibial
valgus while pronating, and only one of the ten (10%),
Subject 04, did not demonstrate subtalar pronation while
allowing tibial valgus. The only occurrences when neither
of these characteristics was noted was when the subject
recovered with knees fully extended rather than allowing
the knees to flex to absorb the impact. However, only two
of the seven subjects (28.6%) who had anecdotally reported
previous injury recovered from jumping with this supposed
problematic position of knees fully extended. Subjects 03,
05, and 10 support this conclusion, since they present with
tibial valgus and subtalar pronation during one or two of
the trials, and with knees fully extended during the other
trial(s). Conversely, Subject 07’s third trial presents
tibial valgus, subtalar pronation, and knee extension
simultaneously.
Of the 10 subjects, seven women (70%) had anecdotally
reported previous history of knee injury. Two of these
33
seven (28.6%, Subjects 04 and 09), injured athletes had
sustained an ACL tear, four (57.1%, Subjects 02, 06, 08,
and 10), had patellar tendonitis, and one (14.3%, Subject
07), had a history of subluxing patella. One of the ACL-
injured women sustained trauma in 1999, and the other in
July of 2004. Three of the four (75%) athletes with
patellar tendonitis had reported a micro-trauma within the
past five months. The athlete with a history of subluxing
patella has not had an occurrence since 1996. None of the
subjects with tendonitis or subluxing patella required
surgery, however, both of the ACL victims necessitated
surgical repair.
All seven subjects (100%) who reported a history of
knee injuries produced tibial valgus, if not both traits,
during jump recovery. Subject 04, with a previous medical
history of the female athlete triad (ACL, MCL, and medial
meniscus), was the only subject to possess only tibial
valgus, not both characteristics. On the other hand,
Subjects 01, 03, and 05, have never sustained knee
pathology, but presented at least one of the traits during
jump recovery. Subject 05 demonstrated both
characteristics during the Overhead Squat.
34
Table 3. Knee Pathology Compared to Standing Posture, Overhead Squat, and Jump Recovery
Posture OH Squat Jump Recovery
Subj#
Knee Injury
Valg Pron ation
Valg Pron ation
Valg Pron ation
Knee Ext
1. X2. X01
X X
3. X1. X X2. X X†02 X X 3. X X1. X X2. *X 03 3. X X1. X 2. X †04 X X 3. X 1. *X 2. X X05 X X X 3. *X 1. X X2. X X†06 X X 3. X X1. X X2. X X†07 X X X X X 3. X X *X1. X X2. X X†08 X 3. X X1. X X2. X X†09 X X X 3. X X1. X X2. X X†10 X X
3. *X____________________________________________ Knee ext indicates that subject landed with knees fully extended. An X indicates presence of the trait. All subjects presented with one of the traits, if not both, during jump recovery. *The only occurrences when neither of these characteristics was noted was when the athlete recovered with knees fully extended. †All seven subjects who reported a history of knee injuries produced tibial valgus, if not both traits, during jump recovery.
35
With regards to menstruation, of the three women who
lacked a normal menstrual cycle, two (66.67%) had never
sustained a knee injury, and of the seven remaining women
who menstruate regularly, six (85.71%) have sustained a
knee injury. This leads to the conclusion that hormonal
changes may effect the physiological factors that affect
knee stability; however, more research would need to be
collected to correlate the menstrual cycle with the time of
injury.
As additional information, the following vertical jump
heights were also recorded in Table 4. No other measures
strongly nor significantly correlate with jump height.
36
Table 4. Vertical Jump Heights for 10 Division II Female Volleyball Athletes
Subj# Jump Height (cm)1. 45.72 2. 52.07 01 3. 52.07 1. 41.91 2. 43.18 02 3. 43.18 1. 36.83 2. 43.18 03 3. 39.37 1. 40.64 2. 43.18 04 3. 43.18 1. 33.02 2. 39.37 05 3. 39.37 1. 35.56 2. 35.56 06 3. 36.83 1. 48.26 2. 49.53 07 3. 49.53 1. 49.53 2. 49.53 08 3. 53.34 1. 31.75 2. 34.29 09 3. 39.37 1. 43.18 2. 44.45 10 3. 46.99
____________________________________________ Additional information showing jump heights of all the participating athletes X = 42.80cm, SD = 5.82cm
37
DISCUSSION
To discuss the findings of this study, the following
sections are presented: (1) Discussion of Results, (2)
Conclusions, and (3) Recommendations.
Discussion of Results
The primary purpose of this study was to investigate
the relationship between standing posture, active hip range
of motion, and postural control in female collegiate
Volleyball athletes. With the increased prevalence of knee
injuries in female athletics, the athletic trainer is faced
with many concerns regarding his/her athletes’ safety and
well-being, especially those working with repetitive
jumping athletes.
Lack of postural control, stemming from core and
lumbo-pelvic hip complex weaknesses, is a suggested cause
of knee injury.3,6 With improper muscle recruitment patterns
in the hip, and possibly even the entire lower extremity,
come muscular imbalances and compensatory movements.
Faulty posture has been noted as a factor in causing these
imbalances.3-5,19 Discrepancies in the hip lead to
discrepancies further down the kinetic chain, such as
38
increased Q-angle, tibial valgus, and subtalar pronation,
posing a lot of stress on the soft tissues of the
vulnerable knee.4,5,12,19
The Overhead Squat and the jump recovery assessments
can be useful tools when evaluating athletes’ functional
movement and neuromuscular control.19,23 The specialist who
is conducting the assessment can appropriately analyze the
athletes’ capabilities of creating force, stabilizing
against force, and reducing the impact of force, which can
be compared to their performance in actual sport. Again,
without a stable core, these impacts may be transferred to
weaker components of the body, like muscles and joints.
According to Lathinghouse and Trimble, Q-angle decreases
with an isometric quadriceps contraction, and the magnitude
of this decrease is dependent upon the magnitude of the Q-
angle at rest.28 An excessive Q-angle may predispose women
to greater lateral displacement of the patella during
rigorous activities and sports in which the quadriceps
muscle is stressed.28 In support of Guerra, an increased Q-
angle, according to this study, does tend to create more
valgus at the tibiofemoral joint; however, it is not the
only reason tibial valgus occurs.26 The only athlete to have
a Q-angle past the normal average was the only athlete to
also possess tibial valgus and subtalar pronation
39
throughout all of the assessments. However, many of the
athletes presented with tibial valgus in the assessments
even without a Q-angle greater than the average of 180.
This information suggests that the incorrect mechanics
likely happen due to improper education on jumping
correctly, compensatory motions possibly resultant from
injury, and lack of postural control of the hip and knee
musculature.7,10,12
Typically, when characteristics such as tibial valgus
and subtalar pronation are observed in standard posture,
one could assume they would be distinguished during
movement. If an athlete does not have the correct muscular
recruitment to stand in an ideal posture, then why would
they not display these patterns in a functional activity?
Chances are, if the characteristics noted during standing
posture are not also noted during functional activity,
these anomalies are structural more so than functional (ie,
an increased Q-angle).3,4,13 Conversely, only subtalar
pronation in standard posture correlated with subtalar
pronation during the Overhead Squat. This does not
specifically support nor refute Lephart’s reasoning that
postural discrepancies of standing posture will be
replicated while in motion.4,13 This could mean that athletes
are finding other ways to control for the unwanted tibial
40
valgus, for example, by limiting hip and knee flexion as
exhibited in the study. According to the data, when an
athlete landed with knees fully extended, and therefore
hips minimally flexed, they did not exhibit the tibial
valgus that may have been presented in the postural
assessment and Overhead Squat. No other correlations were
made between the static measures and the dynamic and
functional measures.
As with Q-angle, active hip range of motion is an
important variable when considering an athletes’ mechanics.
Suitable length-tension relationships are vital when
performing dynamic and functional movements.18,22 If one
muscle or muscle group is too tight, the body will
compensate and potentially cause injury. The same happens
when a muscle or muscle group does not produce the correct
amount of tension. Typically, certain patterns may be
witnessed; if one muscle group is shortened, other muscle
groups may shorten also, and opposing muscle groups may be
lengthened and become less-productive to adjust to this
tightness or over-productivity.18,19,22
In this case, probable characteristics for Volleyball
athletes’ active hip range of motion that may cause them to
present with tibial valgus and subtalar pronation were
considered. Specifically, the following deviations were
41
expected: weak gluteals and external rotators resulting in
decreased hip abduction, extension, and external rotation,
and tight adductors and hip flexors resulting in increased
adduction, flexion, and internal rotation. However, no
subjects followed this pattern precisely. On the other
hand, two of the subjects exhibited all of the desired AROM
relationships except for increased hip flexion. Perhaps
hip flexion is not a significant constituent of this
pattern. While jumping, some athletes may reduce the
amount of hip flexion, and thus knee flexion, to control
the amount of tibial valgus being permitted. This could
also possibly be due to the fact that neutral pelvis was
maintained for the flexion measurements, as well as the
rest of the measurements, but could not be accounted for
during the functional movements. Consequently, some
athletes may subconsciously attempt to correct the faulty
mechanics of the lower extremity by wrongly adjusting the
pelvis from a neutral position. However, the researcher
did not observe for nor document pelvic position during the
Overhead Squat or jump recovery. Roach and Miles did not
report that pelvic position was standardized when
performing their study on the effect of age on hip and knee
AROM.18 Neutral pelvis could be assumed in this case; but in
the event that it was not maintained, it may have skewed
42
the interpretation of the AROM data because additional
motion was permitted in the pelvis when Roach and Miles
performed their AROM assessments.
In support of Hass’s and Ashley’s findings, all ten of
the subjects exhibited one, if not both, of the traits
(tibial valgus and subtalar pronation) during the jump
recovery.10,23 One interesting finding was that the only time
that they did not have signs of the anomalies was when they
landed with knees fully extended. In addition, all seven
of the subjects who had reported a history of knee injury
coincidently demonstrated tibial valgus, if not both traits
during the jump recovery, indicating that this uncontrolled
motion may be a culprit for pathology.
In addition to improper mechanics posing additional
stress on stabilizing structures during functional
activity, hormonal changes have been found to have an
effect on the physiological factors that affect knee
stability, according to Wojtys.9 In support of her
conclusions, two of the three (66.7%) athletes with
amenorrhea had never sustained a knee injury, while six of
the seven (85.7%) regularly menstruating participants had.
These findings seem to support the belief that hormonal
productions present in menstruating women could potentially
weaken the static supports of certain articulations.
43
Conclusions
Q-angle was directly correlated with the presence of
tibial valgus and subtalar pronation during standing
posture, dynamic activity, and functional activity. As
well, subtalar pronation in standing posture was directly
correlated with pronation while squatting. However,
patterns among hip AROM were not as conclusive. Perhaps
this could indicate that a functionally sound performance
of the Overhead Squat and jump recovery is not dependant
upon the subjects’ hip AROM measurements. Otherwise,
subjects’ may subconsciously adjust pelvic position to
compensate for abnormal length-tension relationships
occurring at the hip. Furthermore, all ten of the subjects
exhibited tibial valgus and/or subtalar pronation during
jump recovery, suggesting that females have either not
received proper instruction on correct landing biomechanics
or that they are not neuromuscularly efficient enough to
prevent these faulty biomechanics from occurring.
Additionally, females who menstruate regularly may be more
susceptible to injury due to the physiological effect of
hormones on soft tissues’ stability.
44
Recommendations
The researcher makes the subsequent recommendations
for further study related to this topic. Collection of
data from volleyball athletes of other divisions/schools
should be done to limit bias. The results discussed here
are only applicable to athletes of the California
University of Pennsylvania’s Division II Female Volleyball
team, and are intended to represent comparable athletes.
Q-angle should be also measured in standing, in addition
to supine to see if there is any difference noted. Q-angle
in this position takes into account contraction of the
quadriceps to maintain the standing posture.27,28 According
to Lathinghouse and Trimble, Q-angle decreases with an
isometric quadriceps contraction, and the magnitude of this
decrease is dependent upon the magnitude of the Q-angle at
rest.28 An excessive Q-angle may predispose women to greater
lateral displacement of the patella during rigorous
activities and sports in which the quadriceps muscle is
stressed.28
Pelvic position during squatting and landing should be
analyzed to observe for anterior- or posterior-tiling of
the pelvis to compensate for abnormal length-tension
relationships occurring at the hip. This may further
45
explain why the hip AROM measurements did not have any
significant correlations with the Overhead Squat or jump
recovery assessments.
The menstrual cycle should be compared with time of
injury and time of testing. Hormonal changes have been
linked to ligamentous laxity, and furthermore, to the
incidence of knee injury.14,15 It would be interesting to
personally discover precisely when in the menstrual cycle
women are most vulnerable.
46
REFERENCES
1. Prentice WE. Rehabilitation Techniques for Sports Medicine and Athletic Training. 4th ed. New York, NY: McGraw-Hill Companies Inc., 2004, Ch 10:201-223.
2. Akuthota V, Nadler SF. Core strengthening. Arch Phys Med Rehabil. 2004;85(3 Suppl 1):S86-92.
3. Massie DL, Haddox A. Influence of lower extremity biomechanics and muscle imbalances on the lumbar spine. JOrthop Sports Phys Ther. 1999;4:46.
4. Tiberio D. Pathomechanics of structural foot deformities.
Phys Ther. 1998;68:1840. 5. Krivickas LS. Anatomical factors associated with overuse
sports injuries. Sports Med. 1997;24:132. 6. Mitchell B, Colson E. Lumbopelvic mechanics. British
J Sports Med. 2003;37(3):279-280.
7. Pollard CD, Davis IM, Hamill J. Influence of gender on hip and knee mechanics during a randomly cued cutting
maneuver. Clin Biomech. 2004;19(10):1022-31. 8. Starkey C, Ryan J. Evaluation of Orthopedic and Athletic Injuries. 2nd ed. Philadelphia, PA: F.A. Davis Company, 2002, 71-79, 120-121, 205-207, 244- 268, 285-293, 303-318. 9. Wojtys EM, Huston LJ, Lindenfeld TN, Hewett TE, Greenfield ML. Association between the menstrual cycle and anterior cruciate ligament injuries in female athletes. Am J of Sports Med. 1998;26:614. 10. Hass CJ, Schick EA, Tillman MD, Chow JW, Brunt D, Cauraugh JH. Knee biomechanics during landings: comparison of pre- and post-pubescent females. Med. Sci. Sports Exerc. 2005;37(1):100-107. 11. Harmon KG, Ireland ML. Gender differences in non- contact anterior cruciate ligament injuries. Clin. Sports Med. 2000;19:287-302.
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12. Huston LJ, Greenfield ML, Wojtys EM. Anterior cruciate ligament injuries in the female athlete: potential risk factors. Clin. Orthop. 2000;50-63. 13. Lephart SM, Ferris CM, Riemann BL, Myers JB, Fu FH. Gender differences in strength and lower extremity kinematics during landing. Clin. Orthop. 2002;162-169.
14. Heitz NA, Eisenman PA. Hormonal changes throughout the menstrual cycle and increased anterior cruciate ligament laxity in females. J Athletic Training.
1999;34:144.
15. Cheah SH, Ng KH, Johgalingam VT, Ragavan M. The effects of oestradiol and relaxin on extensibility and collagen organization of the pregnant rat cervix. J Endocrinol.
1995;146:331–337. 16. McLean SG, Lipfert SW, Van Den Bogert AJ. Effect of
gender and defensive opponent on the biomechanics of sidestep cutting. Med Sci Sports Exerc. 2004;36(6): 1008-1016. 17. Norkin CC, White DJ. Measurement of Joint Motion: A
Guide to Goniometry. 3rd ed. Philadelphia,PA: F.A. Davis Co,2003, 176-186.
18. Roach KE, Miles TP. Normal hip and knee active range of motion: the relationship to age. Phys Ther. 1991;71:656 19. Clark MA, Russell AM. NASM OPT: Optimum Performance
Training for the Performance Enhancement Specialist. 1st ed. Calabasas, CA: National Academy of Sports Medicine,
2001, 93-114, 187-241. 20. Kendall FP, McCreary EK, Provance PG. Muscles: Testing and Function. 4th ed. Philadelphia, PA: Lippincott Williams & Wilkins, 1993, 32. 21. Berryman-Reese N, Bandy WD. Joint Range of Motion and Muscle Length Testing. Philadelphia, PA: W.B. Saunders Co., 2002, 49-50. 22. Simoneau GG, Hoenig KJ, Lepley JE, Papanek PE. Influence of hip position and gender on active hip internal and external rotation. J Orthop Sports Phys Ther. 2001;28:158-164.
48
23. Ashley CD, Weiss LW. Vertical jump performance and
selected physiological characteristics of women. Journal of Strength and Conditioning Research. 1994;8:5-11. 24. MF Athletic Company. 2004. Available at
http://www.performbetter.com/detail.aspx_Q_ID_E_4133_A_CategoryID_E_194.
25. Power K, Behm D, Cahill F, Carroll M, Young W. An acute bout of static stretching: effects on force and jumping performance. Med Sci Sports Exerc. 2004;36: 1389-1396. 26. Guerra JP, Arnold MJ, Gajdosik RL. Q-angle: effects of isometric quadriceps contraction and body position. J
Orthop Sports Phys Ther. 2002;19:200. 27. Di Brezzo R, Fort LI, Hall K. Q angle: the relationship with selected dynamic performance variables in women. Clinical Kinesiology. 1996;50(3):66-70. 28. Lathinghouse LH, Trimble MH. Effects of isometric quadriceps activation on the Q-angle in women before and after quadriceps exercise. J Orthop Sports Phys Ther. 2000;30(4):211-216.
49
APPENDIX A
Review of the Literature
50
Introduction
The prevalence of knee injuries is a serious problem
for athletic trainers, particularly those working with
female athletes. Knee injuries have been traced back to
defects such as: lack of core strength, lower-crossed
syndrome, increased Q-angle, genu valgum, pes
planus/pronation, as well as imbalances in flexibility and
functional range of motion.1,2 While core stability and
postural control is a necessary component to every
athlete’s training regimen, its beneficial effects on power
and function have often been ignored.2
The kinetic chain works synergistically to produce
force concentrically, reduce force eccentrically, and
dynamically stabilize isometrically against abnormal
forces. When functionally efficient, each component of
the core disperses weight, absorbs force, and transfers
ground reaction forces.2 Core strength is also mandatory,
specifically in lower extremity dominant sports, to
provide proximal stability while in competition.2,3 If the
distal musculature is strong but the core is weak, there
will not be enough force created to produce or control
efficient movements. A weak core is a typical cause of
inefficient movements that could lead to injury.2,3
51
Neuromuscular efficiency is promoted by the
appropriate combination of postural alignment (static and
dynamic) and stability, which allows the body to absorb
momentum at the correct joint, in the correct plane, and at
the correct time.2 As this efficiency decreases, so does the
body’s ability to react accordingly to abnormal forces.
This could potentially lead to compensation and
substitution patterns, as well as poor posture during
functional activities.4 Pathology of structures within the
neuromusculoskeletal system can result from skeletal
malalignment, which has been defined as either abnormal
joint alignment or deformity within a bone. Pathology can
also result from correlated or compensatory motions or
postures, which may accompany skeletal malalignment.5,6
Consequently, mechanical stress is placed on the static
(ligaments and bones) and dynamic (muscles and tendons)
tissues causing repetitive microtrauma, incorrect
mechanics, and injury.4 Sometimes this overloading of joints
and small muscles is due to the core not sufficiently
contributing to the effort.2 Therefore, stability and
movement are critically dependent on the coordination of
all the muscles surrounding the lumbo-pelvic hip complex.5
It is imperative to link common lower limb skeletal
52
malalignments to their correlated and compensatory motions
and postures.5,6
If more athletic trainers and coaches were aware of
their role in optimal performance, core stability, postural
control, and functional flexibility might be incorporated
more readily into every athlete’s conditioning program.
However, do we as athletic trainers know enough about these
matters to correct improper mechanics and potentially
prevent episodes like these from occurring?
This paper will review: (1) The Importance of Core
Stability, (2) Postural Deviations, (3) Functional Range of
Motion of the Lower Extremity, and (4) Knee Injuries Often
Sustained by Female Jumping Athletes.
Core Stability
Composition of the Core
The core is sometimes referred to as the lumbo-pelvic-
hip complex and is where the human body’s center of gravity
resides. All motion stems from this “core”, comprised of
29 muscles.2,7 To better comprehend what goes into core
training, it is imperative to have a good understanding of
these muscles that supply the entire kinetic chain with
neuromuscular control and efficiency. The core can be
53
thought of as a box with the abdominals in the front, the
paraspinals and gluteals in the back, the diaphragm as the
roof, and the hip musculature as the bottom. Combined,
these muscle groups create stabilization and force-couple
relationships that normal function is dependent upon.2,7
The lumbar muscles that contribute to core
stabilization are the transversospinalis group, erector
spinae, quadratus lumborum, and latissimus dorsi. The
abdominals consist of the rectus abdominis, external
oblique, internal oblique, and transversus abdominis.8 The
transversus abdominis is the most important abdominal
muscle because it is active during all trunk movements and
contracts before any other abdominal prior to the
initiation of any limb motion. The back and abdominal
muscles combined provide sagittal, frontal, and transverse
plane stabilization by controlling forces that are applied
to the body. The core-stabilizing hip muscles are
comprised of the iliacus, psoas, gluteus medius, gluteus
maximus, and hamstrings. Any disruption of these force-
couples can place the body in incorrect alignment and
predispose an athlete to postural imbalances, unnecessary
body aches, and potential injury.8
54
Importance of Core Strengthening
When normal length-tension relationships are
established, the body is provided with an environment to
allow optimal arthrokinematics during functional kinetic
chain movements. The kinetic chain works synergistically
to produce force concentrically, reduce force
eccentrically, and dynamically stabilize isometrically
against abnormal forces.2 When functionally efficient, each
component of the core disperses weight, absorbs force, and
transfers ground reaction forces. Core strength is also
mandatory, specifically in lower extremity sports, to
provide proximal stability while in competition. If the
extremity muscles are strong but the core is weak, there
will not be enough force created to produce efficient
movements. Again, a weak core is a typical cause of
inefficient movements that lead to injury.3
All athletes should incorporate core stability into
their conditioning to gain neuromuscular control, strength,
power, and muscular endurance of the lumbo-pelvic hip
complex. Neuromuscular efficiency is promoted by the
appropriate combination of postural alignment (static and
dynamic) and stability strength, which allows the body to
absorb momentum at the correct joint, in the correct plane,
and at the correct time. As this efficiency decreases, so
55
does the body’s ability to react accordingly to abnormal
forces. This could potentially lead to compensation and
substitution patterns, as well as poor posture during
functional activities.8 Consequently, mechanical stress is
placed on the static (ligaments and bones) and dynamic
(muscles and tendons) tissues causing repetitive
microtrauma, incorrect mechanics, and injury. Therefore,
stability and movement are critically dependent on the
coordination of all the muscles surrounding the lumbo-
pelvic hip complex.
Athletes with poor posture, asymmetries in stance and
gait, chronic or repetitive injuries, overuse or non-
traumatic injuries such as tendonitis, patellofemoral
dysfunction, or non-contact ACL injuries are good
candidates for application of core stabilization.
Sometimes this overloading of joints and small muscles is
due to the core not doing its share of the work.2 However,
before any implementation of strengthening can occur, an
assessment should be performed to provide a basis of the
athlete’s capabilities of core stability.
Assessment of Core Strength and Stability
Prior to the commencement of a core stabilization
program, a baseline assessment should be administered to
56
determine the athlete’s muscle imbalances, arthrokinematic
deficits, core strength, core neuromuscular control, core
muscle endurance, core power, and overall function of the
lower extremity kinetic chain. Since sports activity
involves movement in the sagittal, frontal, and transverse
planes, the core musculature should also be assessed and
trained in these planes. However, the athletic trainer
should try to rid the athlete of asymmetries and incorrect
mechanics before progressing to a more intense, functional
capacity.7,8
Testing for Core Stability. Core strength can be
tested by utilizing the straight leg lowering test. The
athlete is positioned supine with a blood pressure cuff
(inflated to 40 mmHg) placed under the lumbar spine at
approximately L4-L5. The athlete flexes the hips to 900
with the knees in full extension. The athlete is then
instructed to perform a “drawing-in” maneuver (pull
bellybutton to spine) to activate the transversus abdominis
and put the pelvis in a posterior pelvic tilt. The athlete
then lowers the legs toward the table while maintaining a
flat back. The examiner then records the hip angle with a
goniometer when any pressure in the cuff is released.8
Lower abdominal neuromuscular control can be assessed
similarly. The athlete is again placed supine, but with
57
hips and knees flexed to 900, and the blood pressure cuff is
positioned the same. The athlete performs the drawing-in
maneuver and lowers the legs until the cuff pressure
decreases. This test depicts the ability of the lower
abdominals to stabilize the lumbo-pelvic hip complex. At
the point where the pelvis anteriorly tilts, the hip
flexors work as the stabilizers. This causes anterior
shearing and compressive forces at L4-L5 and inhibits the
transversus abdominis, internal oblique, and multifidus, a
common cause of low-back pain. Performing activity with
inhibition of these key stabilizers causes muscle
imbalances and inefficient neuromuscular control in the
kinetic chain.8
Erector spinae performance can be assessed by having
the athlete lie prone with hands crossed behind the head.
The goniometer is adjusted with axis at the axilla,
adjustable arm parallel with the lateral side of the body,
and the stationary arm parallel to the table. The athlete
is instructed to extend at the lumbar spine to 300 and hold
for as long as possible while the athletic trainer times
the test.8
Testing for Core Power. Power of the core can be
tested by performing an overhead medicine ball throw. The
athlete is instructed to hold a 4kg medicine ball between
58
the legs as they squat down. They then jump as high as
possible while simultaneously throwing the ball backward
over their head. The distance is then measured from the
starting line to the point where the medicine ball stops.
This is actually an assessment of total body power
production with an emphasis on the core.7
Although adequate strength, power, muscular endurance,
and neuromuscular control are vital for core stabilization,
performing exercises incorrectly or that are too advanced
for the athlete’s capabilities could be detrimental.
Exercise of the core musculature is more than trunk
strengthening. Motor relearning of inhibited muscles may
be more important than strengthening in some patients, such
as patients with low-back pain. For core stability to be
accomplished, the athletic trainer must first correct this
asymmetrical and compensatory movements.2,7
Strengthening Strategies
A comprehensive core stabilization program should be
systematic, progressive, and functional. It should begin
in the most challenging environment an athlete can control.
The program should be manipulated regularly by altering any
of the following variables: plane of motion, range of
motion, loading parameters (Physioball, medicine ball,
59
bodyblade, weight vest, dumbbell, rubber tubing, etc.),
body position, amount of control, speed of execution,
amount of feedback, duration (sets, reps, tempo, time under
tension), and frequency.9 The following are key concepts for
proper exercise progression: slow to fast, simple to
complex, known to unknown, low force to high force, eyes
open to eyes closed, static to dynamic, correct execution
to increased reps/sets/intensity. The importance of
quality before quantity should be stressed. An athlete who
trains with poor technique and poor neuromuscular control
will develop poor motor patterns and poor stabilization.
The focus of the program must be on function.7,9
Static postural alignment is the first step in the
core stabilization program. The goal is to perform a
posterior pelvic tilt (PPT) to stabilize the pelvis before
adding any additional movements. Abdominal training
without proper pelvic stabilization increases intradiscal
pressure to dangerous levels, causing buckling of the
ligamentum flavum and narrowing of the intervertebral
foramen.9 Motor relearning can be obtained by performing
PPTs 5-10 repetitions every hour, which also reduces the
risk of neuromuscular overloading. Progress the athlete to
decreased foot pressure and reduced hand support to
maintain the position.9 Electromyographic (EMG) recordings
60
display higher abdominal activity, rectus abdominus and
obliques particularly, when a posterior pelvic-tilt was
performed, rather than a drawing-in maneuver (pulling belly
button towards back).10
A fundamental progression uses a single-knee-to-chest
exercise to facilitate the posterior pelvic tilt. The
athlete then lowers the leg to the floor with the knee
flexed at 450, maintaining alignment and contact with the
floor. This can be modified by extending the knee 5-100,
further by sliding the leg across the ground, and even
further by incorporating both knees-to-chest. These
exercises can also be performed on a foam roller to enhance
proprioceptive application.8
Bridging is an exercise that recruits the gluteus
maximus in addition to the lower abdominals. The athlete
must focus on lifting the belly button to the ceiling while
lifting the hips, pelvis, and lower lumbar spine as a unit.
The goal is hip extension to neutral through the hip and
neutral pelvis, with minimal assistance from the feet.
When this is accomplished, the athlete can progress to
single-leg bridging and/or bridging with feet resting on a
Physioball.7
Planks can also be administered. The athlete should
be instructed to support body prone on elbows with a
61
neutral pelvis. To incorporate the obliques, this exercise
can also be done laterally on a single elbow. Quadraped
position, with the athlete on all fours maintaining a
neutral pelvis, is a good exercise for the lumbar
extensors. Progress to extending alternate arms and legs
simultaneously (ie, right arm with left leg, left arm with
right leg), then advance to doing them on a Physioball.
Abdominal exercises that are typically performed on the
floor in the sagittal, frontal, and transverse planes can
also be carried out on the Physioball for a more difficult
routine.7 Execution of any functional activity on an
unstable surface could potentially be though of as “core
stabilizing” since the body must achieve neuromuscular
efficiency to perform the exercise.11
There is a vast assortment of equipment on the market
to directly strengthen the abdominals, such as the Abflex
machine, the AbRoller, the ABslide, the AB-Doer, the Nordic
Track Ab Works, and the Nautilus crunch machine, to name a
few. When surveying the results of EMG recordings,
professionals have suggested that these devices are most
effective if they not only mimic the mechanics of a
traditional crunch, but also provide external resistance to
increase the involvement of the musculature.12-14
62
Postural Deviations
Postural deviations, including muscular imbalances and
neuromuscular discrepancies, can disrupt a person’s
mechanics and possibly induce chronic pains and injury
while participating in sport.2 These imbalances and
functional adaptations need to be corrected to avoid
problematic situations for the athlete, as well as the
athletic trainer.
It is extremely common for an athlete to develop
tightness in their psoas muscle, the main hip flexor. A
tight psoas increases shear force and compressive force at
the L4-L5 junction. A tight psoas also causes reciprocal
inhibition of the gluteus maximus, multifidus, deep erector
spinae, internal oblique, and transversus abdominis. Lack
of lumbo-pelvic-hip complex stabilization prevents
appropriate movement sequencing and causes synergistic
dominance by the hamstrings and superficial erector spinae
during hip extension. This postural defect is commonly
referred to as lower-crossed syndrome and can potentially
lead to hip extensor mechanism dysfunction during
functional movement patterns.3,7 It also decreases the
ability of the gluteus maximus to decelerate femoral
internal rotation during heel-strike, which predisposes an
63
athlete with a knee ligament injury to abnormal forces and
repetitive microtrauma.2
During closed-kinetic chain movements, the gluteus
medius decelerates femoral adduction and internal rotation.
A weak gluteus medius increases frontal- and tansverse-
plane stresses at the patellofemoral and tibiofemoral
joints. It also leads to synergistic dominance of the
tensor fascia latae and the quadratus lumborum, a common
mechanism of iliotibial band and lumbar erector spinae
tightness. The athletic trainer must address the altered
hip muscle recruitment patterns or accept it as an injury-
adaptive strategy and thus accept the unknown long-term
consequences of this dysfunction.2,7 This entails a full
lower extremity range of motion assessment.
Overuse injuries, such as shin splints and
tendonitis, are often caused by abnormal biomechanics of
the lower extremity.5 While we as clinicians may feel more
informed about the effect that lower extremity biomechanics
can have on pathologies ranging from the foot to the hip,
it is also important to consider the effect of lower
extremity biomechanics on the pelvis and lumbar spine.
Abnormal biomechanics may cause compensatory movements that
lead to pathology of the pelvis and lumbar spine. Muscle
imbalances of the hip and/or lower extremity may contribute
64
to the onset of low back pain. Therefore, a comprehensive
evaluation for low back pain should include assessment of
the lower extremity for such abnormalities.8,9
Quadriceps angle, or Q-angle, is defined as the
relationship between the line of pull of the quadriceps and
the patella tendon.15 Women, typically possessing larger
pelvic widths, tend to have a greater Q-angle, thus,
possessing greater tibial valgus which could potentially
increase lateral tracking of the patella.15,16
Motion at the subtalar joint (STJ) consists of
pronation and supination. Pronation is an important
component to STJ range of motion because it provides shock
absorption and allows the foot to adapt to changes in
terrain. Supination is important because it allows the
foot to become a rigid lever for propulsion. During gait,
the STJ influences motion that occurs throughout the lower
kinetic chain by transmitting forces between the foot and
lower extremity.6
Abnormal biomechanics, whether due to acute injury,
structural deformity, or muscle imbalance, will cause the
body to compensate and alter its normal function. For
instance, an athlete with a tight gastrocnemius may lack
sufficient dorsiflexion for gait and will compensate by
toeing-out, or externally rotating the feet, while walking.
65
Often it is compensatory motions such as this that lead to
microtrauma and injury.5
While a certain amount of STJ pronation is needed for
normal gait, excessive or limited amounts of either motion
may contribute to abnormal mechanics which are generated
throughout the lower kinetic chain, pelvis, and lumbar
spine.6
Hyperpronation, or pronation that occurs beyond the
midstance period of the gait cycle, leads to a hypermobile
foot and is commonly identified as a contributor to
pathologies of the entire lower extremity, hip, and
sacroiliac joint.6 This is typically the result of tight
peroneals, gastrocnemius, soleus, and iliotibial band, and
lengthened/weak posterior tibialis, flexor digitorum
longus, flexor hallucis longus, and anterior tibialis.6,7
This common postural defect can be referred to as pronation
distortion syndrome, and may be the culprit for injuries
such as plantar fasciitis, posterior tibialis tendonitis,
medial tibial stress syndrome, anterior knee pain, and low
back pain.7
Conversely, the absence of normal STJ pronation during
gait and functional activity lowers the shock absorption
ability in the lower extremity, pelvis, and lumbar spine.
An athlete who presents with a supinated gait pattern will
66
have a rigid foot, which does not allow for optimal force
attenuation, possibly resulting in overuse injuries and/or
low back pain.5,6
Functional Range of Motion in the Lower Extremity
Muscle inflexibility also predisposes athletes to
the development of a variety of overuse injuries.5
Flexibility deficits may be improved by an appropriate
stretching program. Unfortunately, lower extremity
malalignment is less amenable to intervention. Orthotics
are often prescribed to improve lower extremity
alignment. However, studies have not shown that orthotics
have any effect on knee alignment and, while they can
alter subtalar joint alignment, the clinical benefit of
this remains unclear.4 Awareness of anatomical factors
that may predispose athletes to overuse injuries allows
the athletic trainer to develop individual rehabilitation
programs designed to decrease the risk of overuse injury.
In addition, the clinician can advise the athlete on the
importance of avoiding extrinsic factors that may result
in overuse injury.4
Range of motion of each segment of the lower extremity
must be within normal limits to ensure standard length-
67
tension relationships and ultimately produce regular
arthrokinematics. If one muscle, or group of muscles, is
incapable of proper lengthening, it can create imbalances
throughout the entire kinetic chain.
Typical ranges for ankle range of motion are: 200 of
dorsiflexion, 500 of plantarflexion, 200 of inversion, and
50 of eversion.17 It is common to see athletes with
excessive foot pronation, or adduction and plantarflexion
of the talus and eversion of the calcaneus, while the foot
is weight-bearing. It is sometimes visibly apparent upon
inspection when the medial concavity of the foot drops.
This can be caused either statically or dynamically. The
static deformity is caused by the inefficiency of the
spring ligament, connecting the navicula to the
sustentaculum tali of the calcaneus, to support the medial
longitudinal arch. Dynamically, it can be triggered by
over-activity of the peroneals and inhibition of the
posterior tibialis.18,19 Athletes with this type of posture
are predisposed to medial tibial stress syndrome and other
chronic lower leg pains.
Ranges of motion for the knee include: 135-1450 of
flexion, 0-100 of extension, and minimal rotation of the
tibia at extremes of flexion and extension.17 Genu valgum,
or tibial valgus, is a disorder characterized by “knocked-
68
knees.” With excessive genu valgum, the knees are visibly
closer together than the ankles during stance. Objectively
measuring a person’s Q-angle determines if this condition
is present. It usually occurs because of structural
anomalies secondary to muscular weaknesses at the hip, or
hyperpronation of the feet. Genu valgum can lead to a
variety of different postural deviations in the lower
extremity, such as increased foot pronation, internal
tibial rotation, medial patellar positioning, and internal
femoral rotation.19
Normal hip ranges of motion are as follows: 120-1300 of
flexion, 10-200 of extension, 450 of abduction, 300 of
adduction, 450 of internal rotation, and 500 of external
rotation.17,20,21 When the pelvis is in neutral position,
there is typically an 8-100 angle between the anterior
superior iliac spine (ASIS) and the posterior superior
iliac spine (PSIS). An overly anteriorly tilted pelvis
produces more than 100 difference while an overly
posteriorly tilted pelvis produces less than 80
difference.2,18
The amount of range of motion present in all joints of
males and females appears to differ, but not with respect
of all joints. However, in almost all cases, the greater
amount of range of motion is found in the female
69
population. In a study of 60 college-age subjects
investigating the influences of hip position and gender on
hip rotation, females demonstrated a statistically greater
range of active hip internal and external rotation compared
with males.21 Increased internal, but not external, hip
rotation in females has also been reported by Svenningsen
et al.,20 who studied 761 Norwegian subjects ranging in age
from 4 years to adulthood (the 20s). Other motions of the
hip that have been reported as being increased in females
compared with males are hip flexion and hip abduction in
adolescents and young adults.20
Without normal length-tension relationships, an
athlete is more prone to injury due to improper passive
lengthening and faulty eccentric contraction of the
musculature to absorb the force. It is partially the
athletic trainer’s duty to ensure that his/her athletes are
stretching properly prior to intense activity, especially
those with possible imbalances and discrepancies.
Knee Injuries Sustained by Female Jumping Athletes
Female participation in athletics has increased
dramatically over the last decade. Accompanying the
increase in sports participation is the increase incidence
70
of injury.22 Anterior cruciate ligament (ACL) sprains and
tears, patellar tendonitis, and subluxing patella are just
a few of the typical knee injuries seen regularly in the
jumping, female athletic population. Many of these
occurrences are due to valgus motion of the knee during
jump recovery as a result of muscular imbalances.22
ACL Injury
Rupture of the ACL is one of the most common and
potentially traumatic sports-related knee joint injuries.23
Injury to the ACL results from a force causing an anterior
displacement of the tibia relative to the femur, a
posterior displacement of the femur on the tibia, or from
hyperextension of the knee. The majority of ACL sprains
occur as a result of non-contact rotational stress, such as
when an athlete cuts or pivots, ultimately producing loads
that cannot be supported by bony structures and muscles,
thus leading to large ligament loads.23
Upon evaluation of simulated “game-instances” in a
laboratory setting, it was found that females exhibited
increased knee valgus and foot pronation, and decreased hip
flexion, hip abduction, hip internal rotation, knee
flexion, and knee internal rotation when compared to their
male counterparts.23 Males had more variability in hip
71
rotation, while females had more variability in knee
rotations. With decreased knee flexion in cutting and jump
recovery, comes increased anterior drawer action of the
quadriceps, and furthermore, the hamstring becomes less
capable of protecting the ACL against these detrimental
forces. All of these joint angle differences during
performance can contribute to the gender-based
dissimilarities. If neuromuscular control, rather than
anatomy, is responsible for knee valgus, prevention of ACL
injuries in women may be possible. McLean, Lipfert, and Van
Den Bogert summarize by claiming,
“Increased hip external rotation in females will
cause increased valgus and pronation. With
increased external rotation of the limb, valgus
load becomes more sensitive to the amount of hip
rotation and women compensate for this by
controlling their hip rotation more tightly.
When this control diminishes, due to fatigue or
an unexpected perturbation, valgus may rise to a
level where ACL injury occurs.”23(p 1010)
Women appear to suffer four to eight times the number
of ACL injuries for the same sports as men. Numerous
explanations and hypotheses have been put forth with little
convincing objective evidence.24 A greater Q-angle (normal
72
for females is ~ 180), anterior pelvic tilt, anteverted
hips, genu valgum, genu recurvatum, and subtalar pronation
are some of the anatomical differences that may predispose
a female to knee injury.18,22 Education about proper dynamic
stabilization of the muscles acting on the knee, as well as
hip joint, is vital.
Both intrinsic and extrinsic factors have been
proposed to contribute to the greater knee injury rate in
female athletes compared with their male counterparts.25,26
Specifically, intrinsic factors refer to lower extremity
skeletal malalignments, including excessive Q-angle, genu
valgum, femoral anteversion, and general joint laxity.
However, most of the skeletal variations between males and
females develop only after the rapid growth associated with
puberty. Not surprisingly then, post-pubescent females
suffer the highest rate of lower-limb injury when compared
with both the prepubescent female and male athletes.25-27
Some of the extrinsic factors associated with ACL
injury include motor control strategies, coordination of
movement patterns, and the level of conditioning and
muscular strength. Coincidentally, only recently have
extrinsic factors, such as jumping and landing strategies,
related to ACL injuries, been studied.25,27 Most landing
studies have focused on kinetics, neuromuscular activity,
73
and kinematics in the sagittal plane without regard to
maturation and frontal plane motion. The kinematics of
high-risk landing patterns have been identified and many
components of these parallel the variations in female
structural alignment with altered motion occurring in the
frontal plane.25,27 Recent research in college-aged
participants has identified gender differences in lower
extremity kinematics and kinetics during landing
activities, indicating that female athletes may possess
altered motor control strategies that result in knee
positions in which an ACL injury may occur.25,28 However,
there is a scarcity of information on the landing control
strategies in young pre-adolescent female sport
participants. Perhaps the reduced injury rate in this
population is a result of using landing strategies that are
“safer” than older female participants. Conversely, these
older female athletes may be utilizing landing strategies
that become injurious when changes in the skeletal
architecture are influenced by the onset of
menstruation.25,28
In a study performed to examine the correlation
between static postural faults in female athletes and the
prevalence of noncontact ACL injury, seven variables were
measured: standing pelvic position, hip position, standing
74
sagittal knee position, standing frontal knee position,
hamstring length, prone subtalar joint position, and
navicular drop test (a test comparing distance between the
navicular and the floor in seated and weight-bearing
positions).22 A conditional step-wise logistic regression
analysis revealed that postural defects such as knee
recurvatum, excessive navicular drop, and excessive
subtalar joint pronation proved to be significant
discriminators between the ACL-injured and non-injured
groups. These findings may have implications regarding
rehabilitation techniques in athletic training, encouraging
correction of these postural discrepancies.22
One striking difference between men and women is the
female hormonal cycle.24,29,30 The basis for this cycle is the
endocrine coordination between the hypothalamus,
the pituitary gland, and the ovaries. The coordination
among these centers occurs through the circulatory system
via hormones. During the course of this cycle, the
absolute levels of estrogen and progesterone, and the ratio
of these hormone concentrations, change over the mean
cycle duration of 28 days.24,29
Estrogen, progesterone, and relaxin affect many
tissues and systems distant from the ovarian follicles.29
Estrogen affects soft tissue strength, muscle function, and
75
the central nervous system, but the effects of progesterone
are less well understood. Progesterone can act as a
central nervous system anesthetic, and relaxin can
drastically diminish collagen tension. Interestingly, the
female monthly cycle represents a series of complex
interactions between these hormones, and such interactions
may play a role in the susceptibility of women to serious
knee injuries, especially ACL tears.24,30
In another study designed to investigate the variation
in ACL injury rates during the female monthly cycle, a
significant association was found between the stage of
the menstrual cycle and the likelihood for an ACL injury.24
In particular, there were more injuries during the
ovulatary phase of women with regular cycles (days 10 to
14) than expected. In contrast, significantly fewer
injuries occurred during the follicular phase (days 1 to
9). The increased incidence of ACL injury in women during
the ovulatory phase of the menstrual cycle, when a surge
in estrogen production occurs, suggests that the epidemic
of noncontact ACL tears in female athletes may be related
to hormonal fluctuations.24 The association observed
between the ovulatory phase and the rate of ACL injury is
statistically significant but requires further
investigation to establish its clinical and practical
76
significance.24 As well, females lack the testosterone-
driven boost that males possess to achieve sufficient
hypertrophy.29 Rather than allowing minimal tibial rotation,
a girl’s knee may move in various planes during provocative
motions, posing a lot of stress on the soft tissue
structures.29
Patellar Maltracking, Subluxation, and Dislocation
The onset of patellofemoral dysfunction has been
attributed solely to an increased Q-angle.31 Normal tracking
of the patella within the femoral trochlea depends on the
relationships between the alignment of the femur on the
tibia, the Q-angle, the integrity of the patella’s soft
tissue restraints, foot mechanics, and the flexibility of
the quadriceps, hamstrings, iliotibial band.31
Patellar tracking disorders may be congenital;
however, injury to the patella or knee may cause a
discrepancy in the anatomical structuring. For example, a
lateral dislocation of the patella results in tearing of
the medial restraints, increasing laxity. An injury to the
knee can also cause atrophy of the vastus medialis oblique
(VMO), increasing the amount of lateral patellar glide with
subsequent shortening of the lateral restraints. Other
variables affecting the equation are increased body weight
77
and gait mechanics. The lack of appropriate muscle length
and excessive pronation can also contribute to patellar
maltracking.31
Acute, chronic, or congenital laxity of the medial
patellar restraints or abnormal tightness of the lateral
retinaculum results in increased lateral glide of the
patella, predisposing patients to subluxations and
dislocations. The patella is most apt to dislocate or
subluxate when the maximum strain is placed on the lateral
patellar restraints, normally within the ranges of 20 to 300
of knee flexion or after a valgus blow to the knee.31
Resultant patellar fractures or osteochondral damage may
ensue. Prophylactic bracing and rehabilitation to
strengthen the VMO and hip musculature are noninvasive ways
to correct patellar tracking problems.31 However, some
chronic dislocators would better benefit from a surgical
repair, which involves shifting the patellar tendon
attachment to correct the tracking discrepancies.31
Patellar Tendonitis
Patellar tendonitis most often has an insidious onset
in individuals participating in jumping activities, running
sports, and weight lifting.18 Acute tendonitis can also
occur as a result of a blow to the tendon. Repetitive
78
motions on a biomechanically malaligned extensor mechanism
can result in unequal loads on the extensor tendon.
The most common site of pain associated with patellar
tendonitis is the inferior pole of the patella; however,
pain may also be present at the superior pole in the case
of quadriceps tendonitis (jumper’s knee), in the middle of
the tendon, or at the tendon’s attachment to the tibial
tuberosity.15 Resisted knee extension may increase pain to
the point that strength is inhibited. The end range of
passive knee flexion elicits pain and may result in
decreased quadriceps flexibility. Crepitus can be palpated
in tendons during active or resisted movements. A cho-pat
strap can be worn during activity to disperse the forces
exerted on the tendon itself; however, surgical debridement
of the tendon may be suggested to cases unresolved by the
noninvasive method.15 On the other hand, the incidence of
these overuse injuries could possibly be limited with
proper core strengthening, and treatment by the athletic
trainer would be minimal.
Summary
Biomechanical interaction of the entire lower
extremity, as well as the core, may be important
79
contributors to the risk of knee injury. Understanding the
interaction between trunk motion and those of the lower
limb joints during functional activity may provide further
insight into the resultant injury mechanism.8,23 For
instance, trunk accelerations at contact will have a
significant impact on the coupled hip and knee flexion, and
more than likely, on alternative plane loading at the knee
joint.23 The athletic trainer is responsible for recognizing
muscular imbalances to ensure optimal performance and
possible prevention of injuries altogether.
Posture and flexibility provide a basis for which all
movement occurs.16 For the movement to be optimal, these
primary factors should be assessed and trained in order to
supply an optimal environment for the desired level of
function.16
Females tend to possess a greater Q-angle,15 increased
hip range of motion, and tibial valgus and pronation in
static standing posture, thereby resulting in these same
traits in dynamic and functional postures while
participating in activity.21 These characteristics, in
addition to having weaker musculature, automatically
predispose them to greater risk of knee injury.21 It is our
job, as athletic trainers, to recognize these warning signs
and appropriately rehabilitate our athletes accordingly.
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APPENDIX B
The Problem
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Statement of the Problem
The purpose of this study is to portray the
correlation between standing posture, hip range of motion,
and postural control in female collegiate volleyball
players. The results of this study will hopefully outline
a potential profile for injury prevention in this
susceptible population.
Definition of Terms
The following terms are included to ensure the reader
accurate understanding of key concepts: 18,32
1) Anteverted hips- an inward rotation of the thigh bone,
also known as the femur, causing the knees and feet to
inwardly rotate; “pigeon-toed” gait.
2) Arthrokinematics- the movement of the articular surfaces
in relation to the direction of movement of the distal
extremity of the bone.
3) Closed-kinetic chain- any movement of the kinetic chain
with the distal segment fixed, or meeting sufficient
resistance; weight-bearing.
4) Compensatory movements- accessory motions that occur
due to postural deviations, muscle weakness, or muscle
tightness.
5) Core/Lumbo-pelvic-hip complex- where the human body’s
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center of gravity resides and all motion begins.
6) “Drawing-in” maneuver- pull navel to ground while lying
supine.
7) Force-couple relationships- two forces whose points of
application occur on opposite sides of an axis and in
opposite directions to produce movement.
8) Functional range of motion- the angle through which a
joint moves from anatomical position to the extreme
limit of segment motion in a particular direction.
9) Genu recurvatum- also referred to as “back knee”;
condition wherein the knee is hyperextended such that
the lower extremity curves.
10) Genu valgum/tibial valgus- commonly known as “knock-
knees”; knees are closer to the midline of the body
than normal and closer together than the feet in
standing position; Q-angle smaller than 1700.
11) Kinetic chain- a combination of several joints uniting
successive segments.
12) Length-tension relationships- tension produced by a
muscle compared to the length of the muscle.
13) Lower-crossed syndrome- postural deviation wherein the
pelvis becomes anteriorly tilted due to tightness of
the lumbar extensors and hip flexors, and weakness of
the abdominals and gluteus maximus.
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14) Medial tibial stress syndrome- commonly referred to as
“shin splints” wherein the connective tissues that
connect the soleus and posterior tibialis muscles
to the periosteum of the posteromedial tibia become
irritated and inflamed.
15) Neuromuscular control- the motor response to sensory
input; adjustment of muscles to destabilizing
forces.
16) Pes planus/pronation- combined conditions of
dorsiflexion, eversion, and abduction of the foot;
flattening of the medial longitudinal arch.
17) Proprioception- conscious and unconscious appreciation
of joint position.
18) Quadriceps-angle/Q-angle- the line of pull of the
quadriceps tendon and the patellar tendon with patella
as the center.
19) Reciprocal inhibition- when motor neurons transmit
impulses to muscles, causing them to contract, the
motor neurons that supply their antagonists are
simultaneously and reciprocally inhibited, or prevented
from firing.
20) Synergist- a muscle that contracts at the same time as
the agonist (primary movement muscle).
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21) Synergistic dominance- the synergist replaces the
agonist as the primary mover.
Basic Assumptions
For the purpose of this study, the following
considerations will be assumed:
1) Subjects will put forth their best effort, provided
that they are instructed properly.
2) The Overhead Squat is a valid assessment of overall
dynamic neuromuscular control.
3) The jump recovery is a valid assessment of the
functional mechanics of the vertical jump.
4) Goniometric recordings are a valid and reliable measure
of flexibility and range of motion.
5) Females are more susceptible to knee injuries due to
hormonal differences, increased Q-angle, genu valgum,
and their tendency to recover from a jump with fully-
extended knees.
Limitation of the Study
Results could be limited to those female athletes
participating in Division II collegiate volleyball.
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Significance of the Study
The prevalence of knee injuries in female athletes is
a serious problem for athletic trainers, particularly those
working with female volleyball athletes. Knee injuries
have been traced back to defects such as: lack of core
strength, lower-crossed syndrome, increased Q-angle,
genuvalgum, pes planus/pronation, as well as imbalances in
flexibility and functional range of motion.1,2 While core
stability and postural control is a necessary component to
every athlete’s training regimen, its beneficial effects on
power and function have often been ignored.2 If more
athletic trainers and coaches were aware of their role in
optimal performance, core stability and postural control
might be incorporated more readily into every athlete’s
conditioning program. However, do we as athletic trainers
know enough about core stability and postural control to
correct these improper mechanics and potentially prevent
episodes like these from occurring? This thesis will
attempt to correlate standing posture, hip range of motion,
and postural control in female athletes to possibly promote
incorporation of these vital concepts into rehabilitation
for the purposes of prevention of initial injury, as well
as recurrence of injury.
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APPENDIX C
Additional Methods
87
APPENDIX C1
Informed Consent
88
Informed Consent Form
1. “Catie Dougherty, ATC, who is a Graduate Athletic Training Student, has requested my participation in a research study at this institution. The title of the research is The Relationship between Standing Posture, Functional Hip Range of Motion, and Postural Control in Female Collegiate Volleyball Players.”
2. "I have been informed that the purpose of the research is to correlate postural defects and functional hip range of motion with measures of postural control in the female Division II volleyball athletes." 3. "My participation will involve evaluation of my posture, hip range of motion, and performance of two (2) functional tests (Overhead Squat and vertical jump). It will require one session of approximately 30-40 minutes of my time and will be video-taped for optimal analysis." 4. "Delayed onset muscle soreness (DOMS) is the only foreseeable risk with the performance of this study, however, I will perform the warm-up as advised. This risk is no different than what is possible in a normal volleyball practice session.” 5. "There are no feasible alternative procedures available for this study." 6. “I am aware that performance of the tests will be video- taped for later analysis by only the researcher and the research advisor.” 7. "I understand that the possible benefits of my participation in the research are to contribute to existing research, enhance injury prevention and understand mechanisms of injury, and/or to enhance the rehabilitative process of my withstanding injury.” 8. "I understand that the results of the research study may
be published but that my name or identity will not be revealed. In order to maintain confidentiality of my records, Catie will maintain all documents in a secure location in which only the student researcher and research advisor can access."
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9. "I have been informed that I will not be compensated for my participation."
10. “I have been informed that any questions I have concerning the study or my participation in it, before or after my consent, will be answered by Catie Dougherty, ATC, [email protected], (412)480-6486, and/or Rebecca A. Hess, Ph.D., [email protected], (724)938-4359.
11. “I understand that written responses may be used in quotations for publication but my identity will remain anonymous.” 12. "I have read the above information. The nature, demands, risks, and benefits of the project have been explained to me. I knowingly assume the risks involved, and understand that I may withdraw my consent and discontinue participation at any time without penalty or loss of benefit to myself. In signing this consent form, I am not waiving any legal claims, rights, or remedies. A copy of this consent form will be given to me upon request."
Subject's signature________________________________________ Date _______________
13. "I certify that I have explained to the above individual the nature and purpose, the potential benefits, and possible risks associated with participation in this research study, have answered any questions that have been raised, and have witnessed the above signature." 14. "I have provided the subject/participant a copy of this signed consent document if requested."
Investigator’s signature___________________________________ Date________________
Approved by the California University of Pennsylvania IRB
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APPENDIX C2
Institutional Review Board (IRB)
91
92
93
94
95
APPENDIX C3
General Demographic Information
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Subject #: ________________ Age:__________
Height: __________ Weight: __________
1) Do you have any history of knee injuries? Yes / No
2) If yes, what was the diagnosis?
__ ACL tear
__ Patellar tendonitis
__ Subluxing patella
__ Other
If indicated, what was the date of your last injury?
_________________
3) Have you had knee or ankle surgery? Yes / No
If indicated, which leg? R / L
4) Do you have a regular menstrual cycle? Yes / No
5) First day of last menstruation: ______________
6) Vertical Jump Heights: Trial 1: _____________
Trial 2: _____________
Trial 3: _____________
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APPENDIX C4
Evaluation Form
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Q-Angle and Active Hip ROM
Subject Q-Angle Flex Ext Abd Add IR ER
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Standing Posture/ Overhead Squat/ Jump Recovery/ Static Dynamic Functional
Subj# Valgus Pronation Valgus Pronation Valgus Pron / 1. 2. 3. 1. 2. 3. 1. 2. 3. 1. 2. 3. 1. 2. 3. 1. 2. 3. 1. 2. 3. 1. 2. 3. 1. 2. 3. 1. 2. 3.
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APPENDIX C5
Active Hip Range of Motion
Measurements
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Active Hip Range of Motion (in Degrees)
Motion Mean (SD)
Flexion: 122 (12)
Extension: 22 (8)
Abduction: 44 (11)
*Adduction: *10 (not reported)
Internal Rotation: 33 (7)
External Rotation: 34 (8)
Ref. Roach and Miles33(p32) *Adduction value obtained from Kendall, McCreary, and
Provance34(p32)
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APPENDIX C6
Overhead Squat Assessment
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TOTAL BODY PROFILE Overhead Squat Objective: To observe for total body neuromuscular efficiency, integrated functional strength and functional flexibility Foot and Ankle
Feet flatten (pronate): Y / N � Externally rotate (turn out): Y / N Knees
Knees buckle inward: Y / N � Knees bow outward: Lumbo-Pelvic-Hip Complex
Asymmetrical weight shifting: Y / N � Low back arches: Y / N � Low back rounds: Y / N � Abdomen protrudes: Y / N Shoulder Complex
Shoulder protraction/abduction: Y / N � Shoulder elevation: Y / N � Scapular winging: Y / N Head
Forward Head: Y / N
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ABSTRACT
Title: The Relationship between Standing Posture, Functional Hip Range of Motion, and Postural Control in Female Collegiate Volleyball Players
Researcher: Catherine L. Dougherty Adviser: Dr. Rebecca Hess Purpose: The purpose of this study was to portray any
correlation between standing posture, active hip range of motion, and postural control in female collegiate volleyball players. The results were used to outline a potential profile for injury prevention in this susceptible population.
Methods: Ten members of the California University of
Pennsylvania’s Female Volleyball team participated in the study. The subjects’ Q-angle, active hip range of motion, standing posture, and performance of the Overhead Squat and jump recovery were analyzed for characteristics that would generate a female volleyball players’ profile and could potentially lead to injury. Frequency tables and Pearson Correlations were used to analyze the data.
Findings: The amount of Q-angle can be correlated with
the performance of the assessments. The sole athlete who possessed a Q-angle greater than the average exhibited tibial valgus and subtalar pronation throughout all of the assessments. Subtalar pronation in standing posture can be correlated with pronation while squatting. However, no direct correlation between active hip range of motion, standing posture, and performance of the assessments were reported. Additionally, all ten subjects displayed at least one of the supposed traits during jump recovery. The only incidence when neither trait was exhibited was when the athlete recovered with knees fully extended. All
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seven subjects who reported a history of knee injuries produced tibial valgus, if not both traits, during jump recovery. With regards to menstruation, of the three women who lacked a normal menstrual cycle, two had never sustained a knee injury, and of the seven remaining women who menstruate regularly, six have sustained a knee injury.
Conclusions: Q-angle is directly correlated with the presence of tibial valgus and subtalar pronation during standing posture, dynamic activity, and functional activity.
Subtalar pronation in standing posture can be correlated with pronation while
squatting. However, patterns among active hip range of motion were not as conclusive.
Perhaps this could indicate that a functionally sound performance of the Overhead Squat and jump recovery is not dependant upon the subjects’ active hip range of motion measurements. Otherwise, subjects’ may subconsciously adjust pelvic position to compensate for abnormal length- tension relationships occurring at the hip. Furthermore, all ten of the subjects exhibited tibial valgus and/or subtalar pronation during jump recovery, suggesting that females have either not received proper instruction on correct landing biomechanics or that they are not neuromuscularly efficient enough to prevent these faulty biomechanics from occurring. Additionally, females who menstruate regularly may be more susceptible to injury due to the physiological effect of hormones on soft tissues’ stability.