This study evaluated the effect of foot progression angle on the reduction in knee adduction moment caused by a lateral wedged insole during walking. Twenty healthy, young volunteers walked 10 m at their comfortable velocity wearing a lateral wedged insole or control flat insole in 3 foot progression angle conditions: natural, toe-out, and toe-in. A 3-dimensional rigid link model was used to calculate the external knee adduction moment, the moment arm of ground reaction force to knee joint center, and the reduction ratio of knee adduction moment and moment arm. The result indicated that the toe-out condition and lateral wedged insole decreased the knee adduction moment in the whole stance phase. The reduction ratio of the knee adduction moment and the moment arm exhibited a close relationship. Lateral wedged insoles decreased the knee adduction moment in various foot progression angle conditions due to decrease of the moment arm of the ground reaction force. Moreover, the knee adduction moment during the toe-out gait with lateral wedged insole was the smallest due to the synergistic effect of the lateral wedged insole and foot progression angle. Lateral wedged insoles may be a valid intervention for patients with knee osteoarthritis regardless of the foot progression angle.
Keywords: ankle valgus moment; foot progression angle; knee adduction moment; lateral wedge insole; moment arm.