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Effect of unloading walking shoes on frontal plane foot kinematics in people with medial knee osteoarthritis
Abstracts / Osteoarthritis and Cartilage 24 (2016) S63eS534
S105
162 EFFECT OF UNLOADING WALKING SHOES ON FRONTAL PLANE FOOT KINEMATICS IN PEOPLE WITH MEDIAL KNEE OSTEOARTHRITIS
unknown. Clinicians should be cautious in recommending these types of unloading shoes for people with pre-existing foot/ankle problems.
B.R. Metcalf, K.L. Paterson, T.V. Wrigley, K.L. Bennell, R.S. Hinman. Univ. of Melbourne, Carlton, Australia
163 ASYMPTOMATIC SUBJECTS AT INCREASED RISK FOR KNEE OA DUE TO AGE DEVELOP REDUCED KNEE EXTENSION AND ADDUCTION MOMENTS OVER TIME
Purpose: Knee osteoarthritis (OA) is a major public health problem that causes significant pain and disability. The condition mainly involves the medial tibiofemoral compartment, and increased medial knee joint loading contributes to the development and progression of medial knee OA. Treatment strategies that reduce medial knee loading may be beneficial for medial knee OA. The external knee adduction moment (KAM) is a valid and reliable indicator of medial knee load. We developed unloading walking shoes with laterally stiff midsoles and mild laterally wedged insoles that were designed to pronate the foot in order to reduce the KAM in people with medial knee OA. Our previous work showed that unloading shoes reduces the KAM via a reduced kneeground reaction force lever arm length and lateral shift in the centre of pressure. However, we did not examine in-shoe segmental foot kinematics hence the effects of unloading shoes on foot motion during walking are unknown. Aim: To investigate the immediate biomechanical effects of an unloading walking shoe on frontal plane foot kinematics in people with symptomatic medial knee OA. Methods: Participants: Thirty two community volunteers aged over 50 with symptomatic radiographic medial knee OA (13F (41%), 19M (59%); mean age 61.3 yrs ± 7.8; mean mass 85.9 kgs ± 13.7). A range of exclusion criteria applied, including foot pain. Procedure: Participants underwent gait analysis using the Vicon motion analysis system. Reflective markers were placed on the lower body using the Plug-In-Gait marker set and on the foot using a modified ‘inshoe’ version of the Oxford Foot Model and shoes with “windows” cut out that permitted marker placement directly on the skin of the foot. Participants performed walking trials in i) neutral walking shoes (Gel Odyssey, ASICS Oceania P/L), and ii) unloading walking shoes (Gel Melbourne OA, ASICS Oceania P/L) in random order. Skin markers remained in situ across test conditions. Walking was performed at selfselected pace in each shoe condition; trials not within 5% of the mean pace excluded. Data were averaged over six trials per test condition and normalised to body weight x height (Nm/BWxHt%). Outcomes: Stance-phase rearfoot (expressed in relation to both the global co-ordinate system (lab), and to the tibia) and forefoot peak inversion and eversion, total frontal plane rearfoot and forefoot excursion, first peak KAM (KAM1) and KAM impulse. Statistical analyses: The mean difference (MD) (95% confidence interval, CI) between shoe conditions (unloading minus neutral shoes) was calculated, and groups compared using paired samples t-tests. As lower angles represent eversion, negative MDs represented increased foot eversion with unloading shoes. Results: When referenced to the lab, peak inversion angle was reduced (MD 1.45 degrees; 95%CI e2.21 to 0.69; p<0.001) in unloading shoes, whilst peak eversion angle was increased (MD 1.65 degrees; 95%CI 2.30 to 0.99; p<0.001), and there was no difference in frontal plane excursion (MD 0.19; 95%CI 0.40 to 0.78; p ¼ 0.511). When referenced to the tibia, peak rearfoot inversion was unchanged (MD 0.75 degrees; 95%CI 1.55 to 0.04; p ¼ 0.061) in unloading shoes, but the peak rearfoot eversion angle was increased (MD 1.70 degrees; 95%CI 2.37 to 1.03; p<0.001) and frontal plane excursion was increased (MD 0.95 degrees; 95%CI 0.35 to 1.54; p ¼ 0.003). The forefoot-to-rearfoot angle at peak inversion was unchanged while walking in unloading shoes (MD 0.93 degrees; 95%CI 1.85 to 0.00; p ¼ 0.050), while the peak eversion angle was increased (MD 1.45 degrees; 95%CI 2.13 to 0.76; p<0.001) and frontal plane excursion was unchanged (MD 0.52 degrees; 95%CI 0.59 to 1.63; p ¼ 0.347). Unloading shoes reduced KAM1 by 4.9% (MD 0.22 Nm/BWxHt%; 95%CI 0.31 to 0.14; p<0.001) and KAM impulse by 6.3% (MD 0.09 Nm*s/ BWxHt%; 95%CI 0.11 to 0.07; p<0.001) compared to neutral shoes. There were no differences in gait velocity and stride length between shoe conditions. Conclusions: In comparison to neutral shoes, unloading shoes resulted in a significantly more everted position of the rearfoot and the forefoot during stance phase of gait, consistent with the shoe’s aim. These increases in eversion were achieved mostly without a concomittant increase in frontal plane excursion. The clinical implications of these significant but relatively small increases in foot eversion during gait are
E.F. Chehab y, z, J.L. Asay y, z, T.P. Andriacchi y, z. y Stanford Univ., Stanford, CA, USA; z VA Hlth. Care System, Palo Alto, CA, USA Purpose: Differences in ambulatory mechanics have been associated with early knee osteoarthritis (OA), with the suggestion that changes in gait also occur at an age (>45 years) when the risk for knee OA increases. As such, there is a need to understand the longitudinal nature of these gait changes in individuals at high risk for developing idiopathic knee OA in order to assess the mechanical conditions that may lead to clinical symptoms of OA. The goal of this study was to determine whether there are changes in kinetic gait features that have been associated with early knee OA in an initially asymptomatic cohort (age 45 to 60 years) between baseline and 7-year follow-up. We tested the hypotheses that the time between the baseline and follow-up test was associated with changes in the magnitudes of the first peak knee extension moment (KEM), peak knee flexion moment (KFM), first peak knee adduction moment (KAM1), and second peak knee adduction moment (KAM2), even after adjusting for walking speed and demographic measures. Methods: Following Institutional Review Board approval, 41 asymptomatic subjects (21 female, 20 male) between the ages of 46 and 69 years were tested at baseline, and re-tested an average of 7.1 ± 2.3 years later (Table 1). Baseline exclusion criteria were history of lower limb injury requiring surgery and chronic joint pain; follow-up exclusion criterion was lower limb joint surgery since baseline test. At both time points, walking mechanics was collected using a motion capture system and a force plate to calculate sagittal and frontal plane knee joint kinetics. Three trials were collected at a self-selected speed for each limb and discrete gait features were averaged to produce one mean value per gait feature per limb. Linear mixed effects models were used to assess which fixed effects (time point, age, gender, body mass index, walking speed) were associated with a particular gait feature (KEM, KFM, KAM1, KAM2). Each model used both limbs at both time points for each subject, and allowed for subject-specific random effects to account for multiple data points per subject. The “time point” covariate represents the aging process, and was coded as 0 for baseline tests and with the time between time points for follow-up test. Bonferroni-corrected statistical significance threshold was set at 0.0125 to account for four comparisons. Table 1. Subject demographics and walking speed (mean ± SD) at baseline and follow-up.
Age (years) Body Mass Index (kg/m2) Walking speed (m/s)
Baseline
Follow-up
56.5 ± 6.1 24.9 ± 4.0 1.42 ± 0.24
63.5 ± 7.0 24.3 ± 3.7 1.37 ± 0.20
Results: The time between tests (“time point” measure) was a key metric associated with decreases in the magnitudes of KEM, KAM1, and KAM2 after adjusting for walking speed, age, gender, and body mass index. All moments magnitudes were expressed as positive values such that a negative B coefficients for “time point” indicated a reduction in the magnitude of the knee moment over time. In addition, all four of the gait features tested were especially influenced by differences in walking speed (Table 2). Table 2. Results of mixed effects models. B: unstandardized coefficients; P<0.0125 bolded. KEM (% Bw*Ht)
Time Point (years) Walking Speed (m/s) Age (years) Gender (M vs. F) BMI (kg/m2)
KFM (% Bw*Ht)
KAM1 (% Bw*Ht)
KAM2 (% Bw*Ht)
B
P
B
P
B
P
B
P
0.05 1.37 0.03 0.38 0.03
0.003 0.000 0.020 0.022 0.080
0.05 3.35 0.02 0.28 0.02
0.092 0.000 0.387 0.274 0.423
0.07 1.68 0.01 0.48 -0.05
0.000 0.000 0.501 0.009 0.016
0.10 0.68 0.02 0.63 0.04
0.000 0.004 0.098 0.001 0.051
S105
162 EFFECT OF UNLOADING WALKING SHOES ON FRONTAL PLANE FOOT KINEMATICS IN PEOPLE WITH MEDIAL KNEE OSTEOARTHRITIS
unknown. Clinicians should be cautious in recommending these types of unloading shoes for people with pre-existing foot/ankle problems.
B.R. Metcalf, K.L. Paterson, T.V. Wrigley, K.L. Bennell, R.S. Hinman. Univ. of Melbourne, Carlton, Australia
163 ASYMPTOMATIC SUBJECTS AT INCREASED RISK FOR KNEE OA DUE TO AGE DEVELOP REDUCED KNEE EXTENSION AND ADDUCTION MOMENTS OVER TIME
Purpose: Knee osteoarthritis (OA) is a major public health problem that causes significant pain and disability. The condition mainly involves the medial tibiofemoral compartment, and increased medial knee joint loading contributes to the development and progression of medial knee OA. Treatment strategies that reduce medial knee loading may be beneficial for medial knee OA. The external knee adduction moment (KAM) is a valid and reliable indicator of medial knee load. We developed unloading walking shoes with laterally stiff midsoles and mild laterally wedged insoles that were designed to pronate the foot in order to reduce the KAM in people with medial knee OA. Our previous work showed that unloading shoes reduces the KAM via a reduced kneeground reaction force lever arm length and lateral shift in the centre of pressure. However, we did not examine in-shoe segmental foot kinematics hence the effects of unloading shoes on foot motion during walking are unknown. Aim: To investigate the immediate biomechanical effects of an unloading walking shoe on frontal plane foot kinematics in people with symptomatic medial knee OA. Methods: Participants: Thirty two community volunteers aged over 50 with symptomatic radiographic medial knee OA (13F (41%), 19M (59%); mean age 61.3 yrs ± 7.8; mean mass 85.9 kgs ± 13.7). A range of exclusion criteria applied, including foot pain. Procedure: Participants underwent gait analysis using the Vicon motion analysis system. Reflective markers were placed on the lower body using the Plug-In-Gait marker set and on the foot using a modified ‘inshoe’ version of the Oxford Foot Model and shoes with “windows” cut out that permitted marker placement directly on the skin of the foot. Participants performed walking trials in i) neutral walking shoes (Gel Odyssey, ASICS Oceania P/L), and ii) unloading walking shoes (Gel Melbourne OA, ASICS Oceania P/L) in random order. Skin markers remained in situ across test conditions. Walking was performed at selfselected pace in each shoe condition; trials not within 5% of the mean pace excluded. Data were averaged over six trials per test condition and normalised to body weight x height (Nm/BWxHt%). Outcomes: Stance-phase rearfoot (expressed in relation to both the global co-ordinate system (lab), and to the tibia) and forefoot peak inversion and eversion, total frontal plane rearfoot and forefoot excursion, first peak KAM (KAM1) and KAM impulse. Statistical analyses: The mean difference (MD) (95% confidence interval, CI) between shoe conditions (unloading minus neutral shoes) was calculated, and groups compared using paired samples t-tests. As lower angles represent eversion, negative MDs represented increased foot eversion with unloading shoes. Results: When referenced to the lab, peak inversion angle was reduced (MD 1.45 degrees; 95%CI e2.21 to 0.69; p<0.001) in unloading shoes, whilst peak eversion angle was increased (MD 1.65 degrees; 95%CI 2.30 to 0.99; p<0.001), and there was no difference in frontal plane excursion (MD 0.19; 95%CI 0.40 to 0.78; p ¼ 0.511). When referenced to the tibia, peak rearfoot inversion was unchanged (MD 0.75 degrees; 95%CI 1.55 to 0.04; p ¼ 0.061) in unloading shoes, but the peak rearfoot eversion angle was increased (MD 1.70 degrees; 95%CI 2.37 to 1.03; p<0.001) and frontal plane excursion was increased (MD 0.95 degrees; 95%CI 0.35 to 1.54; p ¼ 0.003). The forefoot-to-rearfoot angle at peak inversion was unchanged while walking in unloading shoes (MD 0.93 degrees; 95%CI 1.85 to 0.00; p ¼ 0.050), while the peak eversion angle was increased (MD 1.45 degrees; 95%CI 2.13 to 0.76; p<0.001) and frontal plane excursion was unchanged (MD 0.52 degrees; 95%CI 0.59 to 1.63; p ¼ 0.347). Unloading shoes reduced KAM1 by 4.9% (MD 0.22 Nm/BWxHt%; 95%CI 0.31 to 0.14; p<0.001) and KAM impulse by 6.3% (MD 0.09 Nm*s/ BWxHt%; 95%CI 0.11 to 0.07; p<0.001) compared to neutral shoes. There were no differences in gait velocity and stride length between shoe conditions. Conclusions: In comparison to neutral shoes, unloading shoes resulted in a significantly more everted position of the rearfoot and the forefoot during stance phase of gait, consistent with the shoe’s aim. These increases in eversion were achieved mostly without a concomittant increase in frontal plane excursion. The clinical implications of these significant but relatively small increases in foot eversion during gait are
E.F. Chehab y, z, J.L. Asay y, z, T.P. Andriacchi y, z. y Stanford Univ., Stanford, CA, USA; z VA Hlth. Care System, Palo Alto, CA, USA Purpose: Differences in ambulatory mechanics have been associated with early knee osteoarthritis (OA), with the suggestion that changes in gait also occur at an age (>45 years) when the risk for knee OA increases. As such, there is a need to understand the longitudinal nature of these gait changes in individuals at high risk for developing idiopathic knee OA in order to assess the mechanical conditions that may lead to clinical symptoms of OA. The goal of this study was to determine whether there are changes in kinetic gait features that have been associated with early knee OA in an initially asymptomatic cohort (age 45 to 60 years) between baseline and 7-year follow-up. We tested the hypotheses that the time between the baseline and follow-up test was associated with changes in the magnitudes of the first peak knee extension moment (KEM), peak knee flexion moment (KFM), first peak knee adduction moment (KAM1), and second peak knee adduction moment (KAM2), even after adjusting for walking speed and demographic measures. Methods: Following Institutional Review Board approval, 41 asymptomatic subjects (21 female, 20 male) between the ages of 46 and 69 years were tested at baseline, and re-tested an average of 7.1 ± 2.3 years later (Table 1). Baseline exclusion criteria were history of lower limb injury requiring surgery and chronic joint pain; follow-up exclusion criterion was lower limb joint surgery since baseline test. At both time points, walking mechanics was collected using a motion capture system and a force plate to calculate sagittal and frontal plane knee joint kinetics. Three trials were collected at a self-selected speed for each limb and discrete gait features were averaged to produce one mean value per gait feature per limb. Linear mixed effects models were used to assess which fixed effects (time point, age, gender, body mass index, walking speed) were associated with a particular gait feature (KEM, KFM, KAM1, KAM2). Each model used both limbs at both time points for each subject, and allowed for subject-specific random effects to account for multiple data points per subject. The “time point” covariate represents the aging process, and was coded as 0 for baseline tests and with the time between time points for follow-up test. Bonferroni-corrected statistical significance threshold was set at 0.0125 to account for four comparisons. Table 1. Subject demographics and walking speed (mean ± SD) at baseline and follow-up.
Age (years) Body Mass Index (kg/m2) Walking speed (m/s)
Baseline
Follow-up
56.5 ± 6.1 24.9 ± 4.0 1.42 ± 0.24
63.5 ± 7.0 24.3 ± 3.7 1.37 ± 0.20
Results: The time between tests (“time point” measure) was a key metric associated with decreases in the magnitudes of KEM, KAM1, and KAM2 after adjusting for walking speed, age, gender, and body mass index. All moments magnitudes were expressed as positive values such that a negative B coefficients for “time point” indicated a reduction in the magnitude of the knee moment over time. In addition, all four of the gait features tested were especially influenced by differences in walking speed (Table 2). Table 2. Results of mixed effects models. B: unstandardized coefficients; P<0.0125 bolded. KEM (% Bw*Ht)
Time Point (years) Walking Speed (m/s) Age (years) Gender (M vs. F) BMI (kg/m2)
KFM (% Bw*Ht)
KAM1 (% Bw*Ht)
KAM2 (% Bw*Ht)
B
P
B
P
B
P
B
P
0.05 1.37 0.03 0.38 0.03
0.003 0.000 0.020 0.022 0.080
0.05 3.35 0.02 0.28 0.02
0.092 0.000 0.387 0.274 0.423
0.07 1.68 0.01 0.48 -0.05
0.000 0.000 0.501 0.009 0.016
0.10 0.68 0.02 0.63 0.04
0.000 0.004 0.098 0.001 0.051