Abnormal Gait
Department of Physical TherapyNEW YORK UNIVERSITY
Historical PerspectiveTendency to classify gait according
to disease or injury state Hemiplegic gait Parkinsonian gait Spastic gait Quadra- or paraplegic gait Amputee gait, etc.
RationaleA specific disease or injury state
manifested as a discrete and clinically describable problem with the mechanics of gait
Our Starting PointWe’ll take a deficit-oriented vs.
disease- oriented approach to abnormal gait analysis
Example: “How might a spastic hamstring on one side, secondary to hemiplegia caused by a CVA, affect gait mechanics?”
AnswerA spastic hamstring may limit step or
stride excursion and/or pelvic transverse rotation
Preferred Rate of AmbulationFree or comfortable walking speedSelf-selected paceRate at which the normal individual
is most energy efficientRange: ~2.5 - 4.0 mph (cadence of
~75 - 120 steps per minute)Will vary from individual-to-individual
Walking Rates - Historical PerspectiveHistorically walking rates classified
as: Slow: ~75 - 90 steps per minute Medium: ~90 - 105 steps per minute Fast: ~105 - 120 steps per minute
Energy Cost vs. Rate
Summary & InterpretationOxygen expenditure is least while
walking at a rate somewhere between ~85 to 110 steps per minute irrespective of stride (or step) length
Individuals tend to gravitate toward a self-selected pace which is most energy efficient for that individual
Enter - The Idea of a ‘Preferred Rate’A preferred rate of ambulation is
a self-selected walking pace that an individual assumes that is most energy efficient
Clinical ImplicationSince there is apparently a rate-
dependent issue that drives gait efficiency the PT should understand that going slower than and faster than the preferred rate will lead to inefficiency and potential stress on the cardiovascular and motor control systems
Why is Gait More Efficient at Preferred Rate?What is the relationship between
energy efficiency and a preferred rate of ambulation?
The Center of Gravity (COG)
COG located at S1 - S2During preferred rate walking the
COG approximates a sinusoidal curve from the: Sagittal perspective - no greater than a
2” peak-to-valley excursion Frontal perspective - no greater than a
2” medial-to-lateral excursion
Path of the COG
Distortion of the Path of the COGA distorted path of the COG will
require mechanical and motor control compensations that will: Disrupt normal timing of events Over-ride normal gait control
Change from ‘automatic’ to ‘manua’l control strategies
Lead to over-correction of gait mechanics
The Result
Increased energy expenditure
A Simple ExampleWalking with a stiff-knee (“stiff-knee
gait”) with a cylinder castDuring stance the HAT will vault over
the fixed foot (especially during mid-stance)
COG will be deflected higher than the usual 2” upward vertical displacement with increased energy cost
Who Walks with a Stiff Knee?Transient knee injury patient (e.g.,
surgical repair of a ligamentHemiplegic with loss of knee controlThe AK amputee with a locked-knee
prosthesisThe BK amputee with poor knee control
Should we consider each case the SAME?
The Control of GaitMotor control options:
‘Manual’ control theory - thinking about having to take a step each time you want to advance the foot forward
‘Automatic control theory - an automatic control system that accounts for gait mechanics without having to think about foot placement and other metrical details
Which one is it?
Think about this...
An Everyday OccurrenceYou’re walking along 23rd Street,
heading west toward your bus stopYou’re thinking about what was
discussed in Kinesiology class todayYou’re also thinking that there is a
lot a traffic and it’s going to take you forever to get home tonight...
QuestionsAre you thinking about foot placement?Are you thinking about how long each
step should be?Are you thinking about trunk and pelvic
rotation in the transverse plane and maintaining reciprocal arm-swing?
Are you thinking about...
AnswerProbably NOT!
Why?Your gait control is on ‘automatic pilot’
When do you have to think about gait control?
When there’s a perturbation
Central Pattern Generator (CPG)CPG - a group of synaptic connections
probably at the spinal cord level which are triggered by an event or condition
When a threshold is met via a triggering mechanism the CPG appears to be activated and takes over automatic control of gait metrics - i.e., you don’t have to think about it
EvidenceSpinalized (cord transected) cats
suspended over a treadmill will walk with an alternating, striding quadripedal gait
Human quadriplegics have also “walked” this way
CPG and Supraspinal InfluenceGait perturbations
Example: Someone walks across your path from the side that you didn’t see
There’s a need to take immediate corrective action to avoid a collision
Supraspinal centers appear to over-ride the CPG and switch to a ‘manual control’ strategy
What Triggers a CPG?There seems to be a close relationship
between activating a CPG for gait control and preferred rate of ambulation
In other words, there is a rate-dependent relationship between normal gait mechanics and its control mechanism
So...
It appears we maintain the path of the COG within very tight limits and therefore expend the least amount of energy by assuming a preferred rate which in turn leads to an activation of a CPG
Think About This...
What’s one of the most common things heard during gait training in a PT clinic?
“Mr. Jones, while you’re walking, I want to go…”
“...very slow!”
What are some possible implications of this?Mr. Jones will be safe - probably won’t
fall and break his hip (good news).Mr. Jones won’t sue you (good news).The path of the COG may be distorted
(bad news).Energy cost may increase (bad news)
Suppose Mr. Jones has a cardiac condition?
What are some possible implications of this?Mr. Jones may never reach his pre-
injury/disease preferred rate of ambulation and therefore never trigger a CPG that automates gait (bad news).
Mr. Jones’ gait may never look ‘normal’ (bad news).
Is it possible that...
…going very slow might actually cause Mr. Jones to lose his balance and fall?
Why?
Factors That Lead to the Initiation of GaitAssume right LE will advance first:
Weight shift to left LE (unloads right hip)Left hip moves into (hyper-) extension and
precedes right hip flexionRight side of pelvis rotates medially
preceding right hip flexionCOG moves over right foot after it’s
advanced
Factors That Lead to the Initiation of GaitSuccessful completion of these
events probably leads to a triggering of a CPG as preferred rate is attained
Gait Training Scenario
Mrs. Flanagan is standing in the parallel bars with her physical therapist, Dudley Doright, getting ready to take a left step to start walking.
We hear the PT say, “Now, Mrs. Flanagan, I want you to put your left foot forward and take a step…”
What wrong with this picture?Where is the patient’s COG relative to
her base-of-support?What is probably the size of the left
step (step length) relative to the right?What impact will this likely have on her
forward velocity?What are the chances of attaining her
pre-injury/disease preferred rate?
Deficit-Oriented Gait AnalysisQuestions:Do diseases/injuries specifically
manifest as a stereotypical gait pattern?
orDoes the disease/injury lead to a
deterioration of control parameters which cause gait deficits?
ResponseIf you believe the latter…it shouldn’t
matter what the patient’s problem is
If you understand the consequence of the disease or injury (loss of motor control, weakness, damaged supportive structures, loss of a part of or an entire limb, etc.)...
…you should be able to anticipate or predict what impact a deficit has on gait irrespective of their state of injury or disease.
Hip Extensors - Stance
Analysis of Deficits Hip Extensors - StanceEarly stance (@
HS) Prevent hip flexion
(jack-knifing)Early stance (HS -
FF) Guide hip into
flexion eccentrically
Early stance (@ HS) weakness/absence Hip/trunk collapses
into flexionEarly stance (HS -
FF) Trunk falls forward
Hip Abductors - Stance
Hip AbductorsPrevent contra-lateral hip from dipping
greater than 5 - 80
Stance-side abductors active
Loss of abductors: Static analysis - + Trendelenburg sign Dynamic analysis - weakness o f abductors
manifests as ‘lurching gait’ (toward stance- side)
Analysis of Deficits Abductors - StanceEarly stance
COG shifts away from stance side LE
Increases moment arm of COG relative to stance side hip
Stance side abductors generate counter-rotational torque to prevent contra-lateral from dropping > 5-80
Early stance weakness/absence Contra-lateral hip
drops > 5-80 Compensation is to
lean (‘lurch’) over stance-side LE
Quadriceps - Stance
Analysis of Deficits Quadriceps - StanceEarly stance (HS -
FF) Guides knee into 200
of flexion eccentrically (controls unlocking of the knee)
Late stance (HR - TO) Controls for knee
flexion (~400 at TO)
Early stance weakness/absence Inability to absorb energy Buckling
Late stance weakness/absence Knee collapse into flexion
-premature flexion into early swing - ‘rubber knee’
Pre-Tibial Group - Stance
Analysis of Deficits Pre-tibial Group - StanceEarly stance (HS -
FF) Lowers forefoot to
floor eccentrically After forefoot
contacts floor- pull tibia forward over foot
Early stance weakness/absence Forefoot slaps to
the floor - ‘drop-foot’ gait
Loss of forward pull of tibia
Plantar Flexors - Stance
Analysis of Deficits Plantar Flexors - StanceLate mid-stance
Concentrically pulls tibia forward
Late stance (HR - TO) Provides propulsive
thrust during push off
Early stance weakness/absence Loss of forward pull
of tibia Loss of forward
thrust - poor transition to early swing
Ankle Stability - Late StanceAnkle less stable and subject to injury
(e.g., sprains) in plantar flexion vs.dorsiflexion Posterior trochlea in mortise Collateral ligaments swing out of collateral
position
Position of ankle during push-off (late stance) = plantar flexed
Analysis of Deficits Peroneals - StanceLate stance (HR -
TO) Dynamically
provide collateral stability to ankle when plantar flexed
Secondary plantar flexor for forward thrust
Late stance weakness/absence Ankle instability
causing medial-lateral movement
Potential for ankle injury - sprains
Poor transition from late stance to early swing
Analysis of Deficits Plantar Intrinsics - StanceLate stance (HR - TO)
Provide medial - lateral stability to MTP joints (especially nos. 1 & 2) - cancels second degree of freedom
Improves forward propulsion and transition to early swing
Late stance weakness/absence Excessive medial -
lateral ‘shimmy’ of hindfoot during HR
Inefficient forward thrust
Paraspinals -Stance
Analysis of Deficits Paraspinals - StanceEarly stance (HS -
FF) & late stance (HR - TO) Prevent forward
flexion of trunk acting on pelvis
Early & late stance weakness/absence Trunk falls forward Loss of head and
neck control
Analysis of Deficits Hip Flexors - SwingLate stance - early
swing (acceleration) Forward flexion of
femur working with plantar flexors to accelerate LE in early swing
Functionally shortens LE (with eccentric action of quadriceps and dorsiflexors) to prevent ‘toe-drag’
Late stance - early swing weakness/absence of forward acceleration after TO
Toe may not clear the floor during swing through Compensate with
circumduction at hip
Dorsiflexors - Swing
Analysis of Deficits Dorsiflexors - SwingMid-to-late swing
(deceleration) Affects ‘toe-up’
concentrically Functionally
shortens LE during swing through
Mid-to-late swing weakness/absence Loss of ‘toe-up’ Compensation
Increased hip flexion - ‘steppage gait’
Circumduction at hip
Hamstrings - Swing
Analysis of Deficits Hamstrings - SwingLate swing
(deceleration) Decelerates tibial
shank Provides for smooth
transition between late stance and early swing
Late swing weakness/absence ‘Impact on terminal
extension’ - knee slapped into extension or hyperextension
Gait in the Elderly Men - Murray, Kory & Clarkson
Gait did not appear vigorous or labored
Gait pattern did not resemble that of patients with CNS damage
Gait was guarded and restrained - attempt to maximal stability and security
Gait in the Elderly Men - Murray, Kory & Clarkson
Gait resembled someone walking on a slippery surface decreased step &
stride legnth wider dynamic BOS increased lateral
head movement decreased rotation
of pelvis
Gait in the Elderly Men - Murray, Kory & Clarkson
toe/floor clearance distance slightly decreased
lower stance-to-swing ratio
decreased reciprocal arm swing more from elbow than shoulder
Spasticity and its Impact on GaitSpasticity - resistance to passive stretch
Results from CNS (UMN) injury/disease Increased source of uncontrolled/poorly
controlled tension Probably due to loss of inhibiting action of
the CNS While tension production may be significant
the time-rate-of-tension development may be delayed
Spasticity & GaitSpastic response may be caused by:
Unexpected quick stretch of muscles Foot contact with floor Supraspinal overlay
Effects: Restrict joint excursion Delay transition from one gait phase to
the next
Spasticity & GaitDubo et al. showed that EMG activity
of spastic muscles increased during mid-stance i.e., there was a loss of phasic control of muscles
Spasticity & Gait ExamplesQuadcriceps
May prevent knee from unlocking during interim between HS and FFKnee maintained in extension leading to a
‘vaulting’ over stance limb or circumduction of hip
Disrupts (timing) transition to mid- and late stance
May prevent LE bending during swing phase
Spasticity & Gait ExamplesPlantar flexors
Increase in spastic tone may limit forward rotation of tibia between MS and POMay locate ground reaction force well behind
knee causing significant flexion moment during late MS and knee buckling tendency
Ankle may be locked up during PO decreasing propulsive thrust forward - inefficient transition from TO to early swing
Spasticity & Gait ExamplesHamstrings
May limit forward swing of LE - decreasing step length
May prevent knee from reaching a terminally extended position just prior to HS
Gait Training - QuestionsIf gait is controlled by a rate-
dependent chain of synaptic connections at the spinal cord level (i.e., a CPG), is it possible for a PT to effect (physiological) changes in the gait control system?
Gait Training - QuestionsIf gait is initiated (and sustained) as
described previously (e.g., unloading of hip, pelvis rotates medially, COG loads over stance foot, etc.), how do we train patients to start walking?
Gait Training - QuestionsWhat impact will ‘assistive devices’
have on gait performance? Parallel bars Walkers Bilateral & unilateral crutches and canes PTs using contact guarding from the
side or behind
Gait Training - QuestionsIf the rhythmic, symmetrical
alternating characteristics of gait are triggered when a patient assumes their preferred rate, will gait symmetry and a ‘normal’ appearing gait be possible if the patient walks substantially slower than her preferred rate?
Gait Training - QuestionsAre all patients’ objectives concerning
walking the same?Are your objectives for Ms. Walksalot, a
39 year old healthy female who broke her ankle two weeks ago in an intensive tennis match, the same as for Mr. Livesinathirdstorywalkup, a frail 87 year old male, with emphysema and a fractured, pinned hip?
Gait Training - QuestionsWhat’s the best thing a PT can say to
their patient while gait training?...
...Probably very little!