Foot-ankle-knee model for foot orthosis

Foot orthoses, for example laterally wedged orthoses, are often used to relieve knee pain and slow the progression of medial knee osteoarthritis. Investigations have been conducted to understand the effectiveness of foot orthoses for relief of the knee joint. However, the loading responses of knee internal structures are difficult to record from experimental studies. Thus, a three-dimensional finite element (FE) model of the human foot-ankle-knee complex was developed to simulate knee joint behavior under orthotic intervention. Subject-specific geometry of the lower extremity was reconstructed from magnetic resonance images. The geometry model generated was imported into ABAQUS for FE modeling. Material properties were obtained from the literature and previous FE work. Laterally wedged orthoses with wedge angles of 0, 5, and 10 degrees were fabricated. Gait analysis data and muscle forces were used as inputs to derive the established FE model. The model was validated through comparison with both in vivo and in vitro experimental data. After validation, the model was applied in a parametric study on the inclination angles of the laterally wedged orthoses. The predictions from the FE model suggested that laterally wedged orthoses with angles of 5 and 10 degrees could diminish the loading in the medial compartment of the knee. With further improvements to the model, together with experimental studies, this research will provide a useful platform for investigating orthotic intervention.