The causes of ankle valgus are as follows: First, ligament injury: It may be due to the injury and relaxation of the medial deltoid ligament, which will weaken the inward turning force of the ankle and reduce the stability of maintaining the inward turning. Second, flatfoot syndrome: When the collapse of the arch occurs in flatfoot, this time there will be protrusion of the inner ankle, heel exostosis, ankle valgus, and protrusion and smallness of the outer ankle on the body surface. Third, muscle strength imbalance: It may be that the strength of the inward and outward turning muscles of the lower limbs is unbalanced, such as the posterior tibial muscle insufficiency, etc., which will cause foot inversion, muscle strength loss, foot exostosis deformity, including the peroneal long and short muscles, which will turn the heel bone outward, and therefore ankle exostosis will occur.