Effect of lateral-wedge insole on the center of foot pressure and lower extremity muscle activity at gait initiation in patients with medial knee osteoarthritis

[Purpose] In clinical settings, patients with knee osteoarthritis often complain of pain at gait initiation. In the present study, we aimed to determine the differences in the center of foot pressure and lower extremity muscle activity at gait initiation in healthy volunteers compared to patients with medial knee osteoarthritis. [Participants and Methods] The study comprised of 10 females without medial knee osteoarthritis (healthy group) and 10 females with medial knee osteoarthritis (medial knee osteoarthritis group). We measured the center of foot pressure trajectory and muscle activity onset times of the tibialis anterior and internal gastrocnemius at gait initiation. Moreover, we examined the effects of insole use in the medial knee osteoarthritis group. [Results] The posterior center of foot pressure displacement was significantly smaller in the medial knee osteoarthritis group (barefoot and insole) than in the healthy group. The anterior center of foot pressure displacement significantly improved with insole use. The muscle activity onset time of the tibialis anterior was significantly delayed in the medial knee osteoarthritis group (barefoot) than in the healthy group. [Conclusion] Postural control decreased at gait initiation in the medial knee osteoarthritis group.