Investigation of biomechanical effect of inverted orthotic insoles on flexible flatfeet

This study investigated the biomechanical mechanisms of inverted orthotic insoles for correcting flexible flatfoot. Clinical experiments demonstrated that a 15° inverted insole can correct the talonavicular coverage angle (TNCA) within the normal range. Patient-specific finite element models validated by TNCA and plantar pressure measurements revealed that inverted insoles reduced stress at the talocalcaneal contact surface by 39% and decreased lateral ligament and plantar fascia tension by 6–13% compared to barefoot conditions. This corrective effect is primarily attributed to the active role of the medial calf muscles, which help alleviate ankle pain and reduce the risk of plantar fasciitis.