Background Flexible flatfoot cause plantar pressure asymmetry due to faulty biomechanics of the foot and ankle complex. Finally, this faulty kinetic leads to the transfer of harmful forces to the proximal joints. As a result, the subjects with flexible flatfoot are exposed to the risk of overuse injuries. The aim of our study is to the effect of foot orthoses on plantar pressure symmetry in taekwondo athletes with flexible flatfoot. Material and Methods We enrolled 30 taekwondo teenage girls with flexible flatfoot. Subjects were randomly assigned to experimental (n = 15) and control (n = 15) groups. The experimental group used silicone foot orthoses with medial longitudinal arch support for 12 weeks. The control group had no intervention. The outcome included the recording of plantar pressure as double-leg with eyes closed. Covariance analysis was used to compare the results between groups. Results The covariance test shows that the experimental group compared to the control group with a high effect size in the right-left plantar pressure symmetry (p = 0.000, ηp2 = 0.779), the forefoot and rear-foot pressure symmetrical of the right foot (p = 0.000, ηp2 = 0.619) and the forefoot and back-foot pressure symmetrical of the left foot (p = 0.000, ηp2 = 0.541) had a significant effect. Conclusions The results show that the foot orthoses application for 12 weeks balanced the plantar pressure through foot posture correction and restored medial longitudinal arch function. Therefore, restoring the medial longitudinal arch function facilitates the Windlass mechanism; Consequently, the plantar pressure and contact in the forefoot, midfoot, and rear foot are balanced.
