Lateral wedges alter mediolateral load distributions at the knee joint in obese individuals

Obesity is the primary risk factor for knee osteoarthritis (OA). Greater external knee adduction moments, surrogate measures for medial compartment loading, are present in Obese individuals and may predispose them to knee OA. Laterally wedged insoles decrease the magnitude of the external adduction moment in Obese individuals but it is unknown how they alter the center of pressure on the tibial plateau. A gait analysis was performed on 14 Obese (avg. 29.3 years; BMI range: 30.3-51.6 kg/m(2) ) and 14 lean women (avg. 26.1 years; BMI range: 20.9-24.6 kg/m(2) ) with and without a full-length, wedged insole. Computed joint angles, joint moments, and knee extensor strength values were input into a musculoskeletal model to estimate center of pressure of the contact force on the tibial plateau. Statistical significance was assessed using a two-way ANOVA to compare the main effects of group and insole condition (α = 0.05). The insole resulted in a significant (p < 0.01) lateral shift in the center of pressure location in both the Obese and Control groups (mean: 2.9 ± 0.7 and 1.5 ± 0.7 mm, respectively). The insole also significantly reduced the peak external knee adduction moment 1.88 ± 1.82 N m in the Control group (p < 0.01) and 3.62 ± 3.90 N m in the Obese group (p < 0.01). The results of this study indicate the effects of a prophylactic wedged insole for reducing the magnitude of the load on the knee's medial compartment in Obese women who are at risk for knee OA development.