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Background: High tibial osteotomy (HTO) reduces the load distribution of the medial compartment by modifying leg alignment. Knee adduction moment (KAM), a surrogate measure of dynamic loading in the knee joint, decreases after HTO. However, leg alignment does not fully account for KAM. Purpose: To assess the association between the pelvis-knee-ankle angle (PKA), a novel radiographic parameter reflecting leg alignment and pelvic width, and KAM and patient-reported outcomes after HTO. Study Design: Cross sectional study; Level of evidence, 3. Methods: PKA is the angle between the line from the midpoint of the anterior superior iliac spine to the center of the knee joint and the mechanical axis of the tibia. In this study, 54 patients with medial compartment knee osteoarthritis and varus alignment who underwent 3-dimensional gait analysis preoperatively and 2 years after medial open-wedge HTO were evaluated. The primary outcomes were hip-knee-ankle angle (HKA), PKA, KAM peaks, and Knee Society Score (KSS). Single and multivariate regression analysis including PKA and KAM peaks as well as other demographic and radiologic factors was performed. Results: HKA was weakly correlated with the first peak KAM ( r = −0.33; P < .01) and second peak KAM ( r = −0.27; P = .01) before HTO, but not significantly correlated after HTO. PKA was moderately correlated with the first peak KAM ( r = 0.45; P < .01) and second peak KAM ( r = 0.45; P < .01) before HTO and with the first peak KAM ( r = 0.51; P < .01) and second peak KAM ( r = 0.56; P < .01) after HTO. Multivariate linear regression revealed that postoperative PKA was still associated with the KAM peaks after HTO. Only postoperative PKA was correlated with the KSS satisfaction subscale ( r = −0.30; P = .03). Conclusion: Although HKA was not correlated with KAM peaks after HTO, PKA was significantly correlated with KAM peaks in patients with varus knee osteoarthritis after HTO.

Background During progression of knee osteoarthritis (KOA), coronal, sagittal, and horizontal biomechanical parameters are dramatically altered. The purpose of this study is to assess the three-dimensional knee joint biomechanics and trunk posture according to KOA severity. Methods Seventy-five patients (95 knees) with medial knee osteoarthritis and 19 young healthy controls (38 knees) were enrolled in this study. The Kellgren-Lawrence classification was used for radiographic evaluation. There were 20 patients with 24 knees with grade 2, 25 with 28 knees with grade 3, and 30 with 43 knees with grade 4. All patients walked at a self-selected speed using an optical motion capture system. Additionally, six-degrees-of-freedom kinematics of the knee joint were calculated using the point cluster technique. The three moment components of the knee joint were calculated using inverse dynamics. Results In grade 2 KOA, the relative contribution of knee adduction moment (KAM) increased significantly, and that of knee flexion moment (KFM) decreased at the first peak of total joint moment prior to significant progression of varus knee deformity. Grade 3 KOA showed significant exacerbation of varus knee deformity and increased KA. Maximum knee extension angle decreased and trunk flexion increased during gait in grade 4 KOA. Conclusions We showed that kinetic conversion occurred in grade 2 KOA prior to varus deformity appearance as in grade 3. Knee flexion contracture and trunk flexion during gait occurred in grade 4 KOA. The relative contribution of KAM increased significantly, and that of KFM decreased prior to progression of varus knee deformity. Trial registration: Not applicable

The effects of foot posture on postural stability and on muscular activation pattern for postural control remain unclear. This study aimed to investigate postural stability and muscular activation onset during the transition task from double- to single-leg stance in individuals with different foot postures. Twenty-seven healthy men (age: 21.5 ± 1.5 years) were divided into 3 groups using the Foot Posture Index: neutral foot (n = 10); flatfoot (n = 8); and high-arched foot (n = 9). Center of pressure (COP) data and muscle activation onset times of the tibialis anterior, peroneus longus, gastrocnemius medialis, and soleus during the transition task with eyes closed were compared among groups using one-way analysis of variance and a post-hoc Tukey honestly significant difference test (p < 0.05) when the data were normally distributed and the Kruskal-Wallis test and a post-hoc Mann-Whitney U-test with Bonferroni correction (p < 0.0167) when the data were not normally distributed. The COP displacements in the mediolateral and anteroposterior directions and the resultant COP displacement during the first 3 s after a stability time point, as determined by sequential estimation during the single-leg stance phase, differed significantly among the three groups (p < 0.05). Post-hoc tests showed that the displacements were significantly greater in the flatfoot group than in the neutral and high-arched foot groups (p < 0.05), and the effect sizes for these results were large. No muscular activation onset times showed significant intergroup differences. Postural stability was significantly decreased only in the flatfoot group, while muscle activation onsets did not differ significantly by foot posture during the transition task. Decreased postural stability may be one mechanism underlying the link between flatfoot and risk of lower limb injury, and foot posture represents a potential confounder for measuring postural stability during the transition task.