The influence of sagittal center of pressure offset on gait kinematics and kinetics Amir Haim a,b,n , Nimrod Rozen c , Alon Wolf a a Biorobotics and Biomechanics Lab (BRML), Faculty of Mechanical Engineering , Technion-Israel Institute of Technology, Haifa, Israel b Department of Orthopedic Surgery B, Sourasky Medical Center, Tel Aviv, Israel c Department of Orthopaedic Surgery, Ha’Emek Medical Center, Afula, Israel article info Article history: Accepted 28 October 2009 Keywords: Center of pressure Coronal kinetics of the knee Footwear-generated biomechanical manipulations Gait analysis Knee flexion torque abstract Objectives: Kinetic patterns of the lower extremity joints have been shown to be influenced by modification of the location of the center of pressure (CoP) of the foot. The accepted theory is that a shifted location of the CoP alters the distance between the ground reaction force and the center of the joint, thereby modifying torques during gait. Various footwear designs have been reported to significantly alter the magnitude of sagittal joint torques during gait. However, the relationship between the CoP and the kinetic patterns in the sagittal plane has not been examined. The aim of this study was to evaluate the association between the sagittal location of the CoP and gait patterns during gait in healthy men. Methods: A foot-worn biomechanical device which allows controlled manipulation of the CoP location was utilized. Fourteen healthy men underwent successive gait analysis with the device set to convey three different sagittal locations of the CoP: neutral, anterior offset and posterior offset. Results: CoP translation in the sagittal plane (i.e., from posterior to anterior) significantly related with an ankle dorsiflexion torque and a knee extension torque shift throughout the stance phase. Likewise, an anterior translation of the CoP significantly reduced the extension torque at the hip during pre- swing. Conclusions: The study results confirm a direct correlation between sagittal offset of the CoP and the magnitude of joint torques throughout the lower extremity. & 2009 Elsevier Ltd. All rights reserved. 1. Introduction During the stance phase of the gait cycle, a force is applied to the ground which is coupled with a ground reaction force (GRF). The magnitude of the GRF is equal and its direction is opposite to the force the body exerts (Winter, 1984). Consequently, joint torques develop which are equivalent to the magnitude of the GRF and the perpendicular distance from the joint center to the force (Gronley and Perry, 1984; Winter, 1984). Theoretically, altering the instantaneous center of pressure (CoP) of the foot would influence the orientation of this force and the resulting joint torques and angles through the body segments. This principle has been the focus of previous research which examined the utilization of footwear-derived biomechanical manipulation. Application of wedge insoles were found to shift the location of the CoP in the coronal plane, thereby altering joint torques from the foot proximally (Kakihana et al., 2005; Maly et al., 2002; Xu et al., 1999) and decreasing the load at the medial compartment of the knee joint in healthy and arthritic subjects (Crenshaw et al., 2000; Kakihana et al., 2005; Ogata et al., 1997; Yasuda and Sasaki, 1987). In a previous study (Haim et al., 2008), we examined the effect of controlled coronal plane CoP modulation at the foot. The magnitude of the knee adduction torque was found to significantly correlate with the coronal orientation of the CoP. Several studies have investigated the effect of sagittal plane footwear modifications on kinematic and kinetic parameters of the lower extremities. Walking with different heel-height shoes has been reported to decrease stride length (de Lateur et al., 1991), to alter joint torques in the lower extremity (Snow and Williams, 1994), and to prolong midstance knee flexor torques during gait (Kerrigan et al., 2005). Missing-heel shoes were found to reduce walking speed and stride length, to increase cadence, and to considerably alter normal ankle joint function (Attinger- Benz et al., 1998). Gait analysis of negative heel rocker sole shoes showed an increase in cadence and a significant alteration of proximal joint metrics (Myers et al., 2006). Similarly, changes in CoP locus were reported with relation to rocker sole ARTICLE IN PRESS Contents lists available at ScienceDirect journal homepage: www.elsevier.com/locate/jbiomech www.JBiomech.com Journal of Biomechanics 0021-9290/$ - see front matter & 2009 Elsevier Ltd. All rights reserved. doi:10.1016/j.jbiomech.2009.10.045 n Corresponding author at: Biorobotics and Biomechanics Lab (BRML), Faculty of Mechanical Engineering, Technion-Israel Institute of Technology, Haifa 32000, Israel. Tel.: + 972 52 4262129. E-mail addresses: [email protected], [email protected] (A. Haim). Journal of Biomechanics 43 (2010) 969–977
The influence of sagittal center of pressure offset on gait kinematicsand kinetics
Amir Haim a,b,n, Nimrod Rozen c, Alon Wolf a
a Biorobotics and Biomechanics Lab (BRML), Faculty of Mechanical Engineering , Technion-Israel Institute of Technology, Haifa, Israelb Department of Orthopedic Surgery B, Sourasky Medical Center, Tel Aviv, Israelc Department of Orthopaedic Surgery, Ha’Emek Medical Center, Afula, Israel
a r t i c l e i n f o
Article history:
Accepted 28 October 2009Objectives: Kinetic patterns of the lower extremity joints have been shown to be influenced by
modification of the location of the center of pressure (CoP) of the foot. The accepted theory is that a
shifted location of the CoP alters the distance between the ground reaction force and the center of the
joint, thereby modifying torques during gait. Various footwear designs have been reported to
significantly alter the magnitude of sagittal joint torques during gait. However, the relationship
between the CoP and the kinetic patterns in the sagittal plane has not been examined. The aim of this
study was to evaluate the association between the sagittal location of the CoP and gait patterns during
gait in healthy men.
Methods: A foot-worn biomechanical device which allows controlled manipulation of the CoP location
was utilized. Fourteen healthy men underwent successive gait analysis with the device set to convey
three different sagittal locations of the CoP: neutral, anterior offset and posterior offset.
Results: CoP translation in the sagittal plane (i.e., from posterior to anterior) significantly related with
an ankle dorsiflexion torque and a knee extension torque shift throughout the stance phase. Likewise,
an anterior translation of the CoP significantly reduced the extension torque at the hip during pre-
swing.
Conclusions: The study results confirm a direct correlation between sagittal offset of the CoP and the
magnitude of joint torques throughout the lower extremity.
& 2009 Elsevier Ltd. All rights reserved.
1. Introduction
During the stance phase of the gait cycle, a force is applied tothe ground which is coupled with a ground reaction force (GRF).The magnitude of the GRF is equal and its direction is opposite tothe force the body exerts (Winter, 1984). Consequently, jointtorques develop which are equivalent to the magnitude of the GRFand the perpendicular distance from the joint center to the force(Gronley and Perry, 1984; Winter, 1984). Theoretically, alteringthe instantaneous center of pressure (CoP) of the foot wouldinfluence the orientation of this force and the resulting jointtorques and angles through the body segments.
This principle has been the focus of previous research whichexamined the utilization of footwear-derived biomechanicalmanipulation. Application of wedge insoles were found to shiftthe location of the CoP in the coronal plane, thereby altering joint
ll rights reserved.
hanics Lab (BRML), Faculty of
f Technology, Haifa 32000,
torques from the foot proximally (Kakihana et al., 2005; Maly et al.,2002; Xu et al., 1999) and decreasing the load at the medialcompartment of the knee joint in healthy and arthritic subjects(Crenshaw et al., 2000; Kakihana et al., 2005; Ogata et al.,1997; Yasuda and Sasaki, 1987). In a previous study (Haim et al.,2008), we examined the effect of controlled coronal plane CoPmodulation at the foot. The magnitude of the knee adductiontorque was found to significantly correlate with the coronalorientation of the CoP.
Several studies have investigated the effect of sagittal planefootwear modifications on kinematic and kinetic parameters ofthe lower extremities. Walking with different heel-height shoeshas been reported to decrease stride length (de Lateur et al.,1991), to alter joint torques in the lower extremity (Snow andWilliams, 1994), and to prolong midstance knee flexor torquesduring gait (Kerrigan et al., 2005). Missing-heel shoes were foundto reduce walking speed and stride length, to increase cadence,and to considerably alter normal ankle joint function (Attinger-Benz et al., 1998). Gait analysis of negative heel rocker soleshoes showed an increase in cadence and a significant alterationof proximal joint metrics (Myers et al., 2006). Similarly,changes in CoP locus were reported with relation to rocker sole
A. Haim et al. / Journal of Biomechanics 43 (2010) 969–977970
shoes (Xu et al., 1999). However, much of the above-mentionedresearch utilized footwear modifications that introduced con-siderable alterations to the normal functioning of the ankle.
The purpose of the current study was to assess the effectof the sagittal CoP position on kinetic and kinematic parametersof the lower extremities. Utilizing a novel foot-worn biomecha-
Table 1Demographic data of participants (n=14).
Age (years) Height (cm) Weight (kg)
25.9572.483 177.3573.52 74.0474.12
Note: Values are mean7SD
Fig. 1. Biomechanical platform and mobile elements. Notes: The biomechanical
device utilized in the study, comprising four modular elements attached onto foot-
worn platforms (APOS system, Apos—Medical and Sports Technologies Ltd.). The
device consists of two convex-shaped biomechanical elements attached to each of
the feet. Each element can be individually calibrated (Position, convexity, height
and resilience) to induce specific biomechanical challenges in multiple planes. The
elements are available in different degrees of resilience and convexity, and are
attached to the subject’s foot using a platform in the form of a shoe.
Fig. 2. A. Biomechanical device at neutral sagittal configuration, B. at anterior configura
the biomechanical elements (red spheres) are transposed anterior and posterior in
interpretation of the references to colour in this figure legend, the reader is referred to
nical device which allows controlled manipulation of the CoP,we hypothesized that translation of elements in the sagittalplane (i.e., from posterior to anterior) would result in amatching alteration of the magnitude of lower extremitysagittal joint torques and kinematic patterns during the stancephase.
tion, C. at posterior configuration. In the anterior and the posterior configurations
relation to the neutral configuration conveying matched offset of the COP. (For
the web version of this article.)
Fig. 3. Representative subject’s CoP relative offset at the posterior, neutral and
anterior configurations. The Y axis represents the vertical distance between the
instantaneous location of the CoP of the instantaneous axis heel axis (perpendi-
cular to the heel to axis crossing the heel marker. (All values are reported in mm
and negative values indicate lateral offset). The X represents 100% of stance phase
time.
Table 2Spatio-temporal parameters, group values (n=14).
extension at terminal-stance (TS); cn—peak hip flexion at loading response (LR); cnn—pe
this figure legend, the reader is referred to the web version of this article.)
posterior condition compared to the anterior condition; however,this was not statistically significant (Table 2).
3.2. CoP trajectory
The CoP trajectory throughout stance shifted in accordance tothe offset of the biomechanical elements (Fig. 3). Inter-subjectanalysis revealed a significant relationship between CoP locusthroughout stance and the sagittal offset of the biomechanicalelements from the neutral position (Table 3).
3.2.1. Sagittal plane kinematics
There were significant differences in ankle, knee andhip kinematics between the three test conditions (Table 4,Fig. 4a–c).
Ankle: Sagittal plane ankle total range of motion (RoM) wassimilar for all conditions tested. At IC, the ankle was slightlydorsiflexed in all conditions tested (3.741�2.211 on average).Anterior and posterior offset significantly related with greater andlesser dorsal flexion, respectively, on average, 1.53–6.3% of totalRoM. Immediately after IC, during LR, the ankle planter flexed. Peakplantar flexion was significantly greater in the posterior conditionthan in the anterior condition, on average, 5.75–23.6% of total RoM.During MS, the joint dorsal flexed. Peak dorsal flexion at the end ofMS was not statistically significant for the three walking conditions.Finally, during PS, the ankle plantar flexed once more. Prior to TC,peak plantar flexion was significantly greater in the anteriorcondition than in the posterior condition, on average, 3.88–15.9%of total RoM.
**
*
0 10 20 30 40 50 60 70 80 90 100
-10
0
10
20
30
40
Knee Hip
50 60 70 80 90 100
it Cycle
int kinematics
kinematics for the three walking conditions tested: neutral (yellow), anterior (red)
ents 100% of a single gait cycle. Data was sampled at the following: the intersection
on at pre-swing (PS); bn—peak knee flexion at midstance (MS); bnn—peak knee
ak hip extension at pre-swing (PS). (For interpretation of the references to colour in
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A. Haim et al. / Journal of Biomechanics 43 (2010) 969–977 973
Knee: Sagittal plane knee total RoM was similar in allconditions tested. At IC, knee extension was on average 1.211(5.8% of total RoM) greater for the posterior condition than for theanterior condition. During LR phase, the knee flexed for the firsttime. Peak knee flexion (during early MS) was similar for the threewalking conditions. Following this flexion peak, the kneeextended. Peak knee extension at TS was slightly greater withthe posterior shoe configuration (on average, 1.18–1.96% of totalRoM) than in the anterior condition. Finally, during PS, the kneeflexed for the second time and knee flexion was on average 6.811(11.2% of total RoM) greater at TC in the anterior condition than in
Peak hip flexion torque at loading response (N m/kg) 5.67 4.77
Peak hip extension at pre-swing (N m/kg) �12.81 4.45
the posterior condition. Peak knee flexion occurring during theswing phase was similar for all walking conditions.
Hip: At IC, hip flexion was on average 1.971 (4.58% of totalRoM) greater in the posterior condition than in the anteriorcondition. Peak hip flexion (during the end of LR and early MS)was on average 1.61 (3.72% of total RoM) greater in the posteriorcondition than in the anterior condition. During mid and TS phase,the hip extended. Peak hip extension (during the end of TS andearly PS) was similar in all conditions tested. At TC, the hip flexionwas on average 3.171 (7.37% of total RoM) greater in the anteriorcondition than in the posterior condition.
****
50 60 70 80 90 100
nt kinetics
*
*
ait Cycle
**
0 10 20 30 40 50 60 70 80 90 100-1100
-1000
-900
-800
-700
-600
-500
-400
-300
-200
-100
0
100
200
300
400
500
600
nee Hip
kinetics for the three walking conditions tested: neutral (yellow), anterior (red),
a single gait cycle. The intersection of the curve with Y axis represents initial foot
er flexion torque at loading response (LR); ann—peak ankle dorsal flexion torque at
ee flexion torque at midstance (MS); bnnn—peak knee extension torque at terminal
ue at loading response (LR); cnn—peak hip extension torque at pre-swing (PS). (For
the web version of this article.)
Neutral Posterior p
ev. Mean Std. Dev. Mean Std. Dev.
�4.15 1.85 �2.69 1.46 0.000
7.43 4.45 8.52 4.60 0.000
28.275 4.49 31.44 4.75 .202
�1.55 2.47 �1.09 2.48 0.000
18.79 6.91 18.3 6.86 .007
3.05 3.33 3.44 3.19 0.000
0.64 0.74 0.24 0.72 .004
�2.29 1.19 �2.81 0.90 0.000
21.44 2.31 20.99 2.20 0.223
5.76 4.91 5.52 5.71 0.607
�13.33 6.09 �14.09 5.54 0.001
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3.2.2. Sagittal plane kinetics
There were significant differences in ankle, knee and hipkinetics between the three test conditions (Table 5, Fig. 5a–c,Figs. 6–8).
Ankle: A significant correlation was found between the deviceconfiguration and the ankle torque at LR and at TS (Table 6). At IC(Fig. 5a), ankle dorsal flexion torque was lower by 0.41 N m/kg forthe posterior configuration, as compared to the anteriorconfiguration, a 63% reduction (Fig. 6, Table 5). Following IC,during LR, the reaction force passes behind the joint and generatesa plantar flexion torque about the ankle. Peak plantar flexiontorque (during LR) was on average 2.17 N m/kg greater for theposterior condition than for the anterior condition, a 77.22%increase. During midstance and TS, the reaction force passes infront of the joint center. The joint sagittal plane external torque istransformed to a dorsal flexion torque. Peak dorsal flexion torque(at the end of TS and the beginning of PS) was 1.05 N m/kg greaterin the anterior condition, a 4.76% rise.
Knee: A significant correlation was found between the deviceconfiguration and the knee torque throughout the stance phase(Table 6). Immediately after IC, the reaction force passes in frontof the knee (Fig. 5b). On average, the peak torque was 2.15 N m/kggreater for the anterior condition, a 44.42% rise (Fig. 7, Table 5).During MS, the line of action passes behind the knee and thetorque reverses into a flexion torque. This torque peaks early inMS with the peak flexion angle of the knee. The peak torque was
Sagi
ttal t
orqu
e (N
m/K
g)
-10
-8
-6
-2
-4
0
2
0
5
10
15
-
-
20
0
5
10
15
20
-5 0
30
20
10
-
Anterior Neutral Posterior
Loading response Mid stance
Anterior Neutral Posterior
Sagi
ttal j
oint
ang
le (°
)
Fig. 6. Knee kinetics and kinematics during stance phase stages. Notes: relationship b
cycle and concomitant joint sagittal angles. Data presented as box-plots—line in center o
and the whiskers represent the range.
1.97 N m/kg lower for the anterior condition than for theposterior condition, a 23.12% reduction. During TS, as the centerof mass passes the base of support, the reaction force once againpasses in front of the knee and the torque reverses into anextension torque. The magnitude of the peak torque was1.12 N m/kg greater for the anterior condition than for theposterior, a 50.6% change. In two subjects, the sagittal kneetorque remained flexed with the posterior configuration through-out the entire stance period. These subjects were excluded fromthe analysis of flexor/extensor torque duration. For the remaining12 subjects extensor torque was significantly longer with theanterior shoe configuration and the flexor torque was shorter,although this difference was not statically significant (Table 5).Throughout PS, the reaction force passes just behind the jointcenter and induces a flexion torque; the peak torque was 1.181less for the anterior configuration in comparison to the posteriorconfiguration, a 34% reduction.
Hip: A significant correlation was found between the deviceconfiguration and the hip torque at MS (Table 6). At IC, the GRFpasses in front of the hip, bringing on a flexion sagittal torque.This torque peaks during LR (Fig. 5c). The magnitude of the torquewas similar in the three walking conditions. The torque thendiminishes and transforms into an extension torque which peaksduring PS. On average, the peak extension moment was 1.28 N m/kg lower for the anterior configuration compared to the posterior,a 9.08% reduction (Fig. 8, Table 5).
etween group joint sagittal moment values throughout consecutive stages of gait
f box represents the median peak value; the box represents the interquartile range
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4. Discussion
The results presented indicate a clear association between themagnitude of lower extremity kinetic parameters and the positionof the CoP in the sagittal plane. The present study examined theoutcome of a controlled shift of the CoP in healthy subjects.Several footwear-generated biomechanical manipulations (e.g.,high heels, reverse heel, rocker bottom) have been shown toinfluence movement patterns in the sagittal plane. However,these interventions introduce vigorous interference to anklekinematics. To the best of our knowledge, this is the first studyto utilize a biomechanical device which allows controlledmodulation of the center of pressure.
We found that anterior translation of the CoP in the sagittalaxis correlated with an ankle dorsal flexor and a knee extensionshift of the sagittal torque throughout the stance phase, a reducedextension torque at the hip during PS and a prolonged duration ofthe terminal stance knee extension torque. A reverse outcomewas found with posterior CoP translation. These findings confirm
Anterior Neutral Posterior Anterior Neu
-1
0
1
2
3
-4
-2
0
0
5
10
-5-15
0
-5
-10
5
10
Sagi
ttal j
oint
ang
le (°
)
2
Initial-contact Loading
Sagi
ttal t
orqu
e (N
m/K
g)
Fig. 7. Ankle kinetics and kinematics during stance phase stages. Notes: relationship b
cycle and concomitant joint sagittal angles. Data presented as box-plots—line in center o
and the whiskers represent the range.
the study’s hypothesis of a direct correlation between the sagittallocation of the CoP and the magnitude of lower extremity sagittaljoint torques. We speculate that the sagittal shifted CoP reducedor extended the distance between the GRF and the center of thejoints throughout successive stages of the stance phase, resultingin reduced or increased magnitude of the torques.
Kinematic patterns of the ankle, knee and hip joints were alsofound to be influenced by a sagittal shift of the CoP. Sagittaltranslation of the CoP from posterior to anterior offset correlatedwith a flexion shift of the knee kinematic patterns and witha bimodal pattern of the ankle and hip kinematics (ankle plantarflexion/hip extension during initial stance and ankle dorsal flexion/hip flexion during final stance). Kerrigan et al. (2005) examined theeffect of high-heeled shoes on gait parameters in healthy womenand reported a 20.41 increase in ankle plantar flexion throughoutthe gait cycle. In the present study, the effect of anteriorand posterior CoP translation on ankle kinematics was lessprofound. Preserving normal ankle function enables a controlledsetting for easement of CoP influence on kinetic parameters.
tral Posterior Anterior Neutral Posterior
26
24
22
20
18
16
-10
0
10
20
-20
-30
response Pre swing
etween group joint sagittal moment values throughout consecutive stages of gait
f box represents the median peak value; the box represents the interquartile range
A. Haim et al. / Journal of Biomechanics 43 (2010) 969–977976
Kerrigan et al. (2005) reported greater peak knee flexion,prolonged knee flexor torque and reduced peak knee-extensortorque with high heels. In the present study, posterior CoP offsetcorrelated with similar kinetic findings (i.e., greater and pro-longed knee flexor torque and reduced shorter peak knee-extensor torque). The knee sagittal torque significantly correlatedwith the knee flexion angle. Interestingly, with posterior offsetconfiguration, knee angles were not significantly different duringmidstance and were more extended during terminal stance. Thissuggests that the altered kinetics recorded with the posterioroffset is a result of altered position of the GRF and is not caused byaltered joint kinematics (i.e., increased knee flexion angles withposterior CoP offset could have accounted for the greater flexortorque).
Several limitations arising from the current study should benoted. First, the relative CoP location was analyzed indirectly bycalculating instantaneous force plate recorded COP and corre-sponding foot segment axis distance. While, this method offers areasonable evaluation of the COP offset and was utilized inprevious studies (Haim et al., 2008), future studies incorporatingdirect COP measurement (e.g., pedobarograph analysis) couldprovide valuable data regarding shoe COP pattern modulation.Another limitation of this study was the employment of theapparatus at neutral position as a control. This setting wasselected to assure consistency of the kinematic model. Finally, itshould be emphasized that the participants in this studycomprised a distinctive homogenic cohort of healthy young maleadults. These results are therefore valid only for individuals withcharacteristics similar to those of the tested group. Differentpopulations (e.g., females who tend to have different lowerextremity joint motions compared to males due to anatomical,muscle strengths, ligament properties) may respond differently tosuch interventions. Further studies are needed before thesefindings can be validated in other populations.
The results of the present study offer clinically relevantimplications to several musculoskeletal pathologies. The knee
Anterior Neutral Posterior
1; (.000)
.670; (.009) 1; (.000)
.612; (.020) .504;(.066) 1; (.000)
1; (.000)
.943; (.000) 1; (.000)
.701; (.005) .635; (.015) 1; (.000)
1; (.000)
.824; (.000) 1; (.000)
.783; (.001) .909; (.000) 1; (.000)
1; (.000)
.873; (.000) 1; (.000)
.605; (.022) .739; (.003) 1; (.000)
1; (.000)
.974; (.000) 1; (.000)
.842; (.000) .899; (.000) 1; (.000)
1; (.000)
.952; (.000) 1; (.000)
.903; (.000) .934; (.000) 1; (.000)
1; (.000)
.912; (.000) 1; (.000)
.965; (.000) .960; (.000) 1; (.000)
1; (.000)
.873; (.000) 1; (.000)
.405 (.151) .431 (.124) 1; (.000)
1; (.000)
.982; (.000) 1; (.000)
.915; (.000) .924; (.000) 1; (.000)
ce; TS—terminal stance
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flexion moment during MS is proportional to the pressure acrossthe patellofemoral joint and has been linked with patellofemoralpain syndrome (PFPS) and osteoarthritis (OA) of the knee(Kerrigan et al., 1998). Similarly, it has been suggested (Astephenet al., 2008) that interventions designed at altering knee kineticsmay be effective for halting progression of knee OA. Secondly, inanterior curciate ligament (ACL)-deficient knees, internal momentgenerated by quadriceps contraction can cause excessive anteriortibial translation. It has been suggested that this motion can leadto premature knee osteoarthritis. A reduction in the peak kneeflexion moment coupled by a reduced internal quadricepsmoment has been reported to be a necessary compensation toavoid excessive anterior translation of the tibia (Andriacchi andDyrby, 2005). Finally, patients suffering from cerebral palsy andother neurological pathologies often experience difficulty main-taining upright posture due to a reduction in the total supportmoment (Lampe et al., 2004). Biomechanical manipulation via Afootwear design that incorporates anterior CoP offset may inducean extension shift to the sagittal torque and provide benefit tothese patients. An extension shift to the sagittal torque couldtheoretically lower patellofemoral joint pressure in knee OApatients, diminish excessive anterior tibial translation in patientswith ACL deficient knees, and contribute to total support momentin patients with cerebral palsy. However, such interventionsshould be taken with caution; excessive extension shift to thesagittal torque could possibly alter joint kinematics. it should bementioned that an extension shift to the sagittal torque may notbe safe for the knee. A reduced tendency to flex the knee canreduce the knee joint’s capacity for shock absorption and wouldlikely aggravate the tibiofemoral contact stresses at the articularcartilage. Further studies examining the benefit and safety ofmoderate anterior CoP offset alterations in patients with theabove pathologies are warranted.
Conflict of interest statement
No author has any conflict of interest to declare.
Acknowledgment
The authors thank APOS—Medical and Sports TechnologiesLtd. for their generosity in contributing the devices used in thestudy.
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