Subtalar Joint Biomechanics: From Normal to Pathologic.

Subtalar joint biomechanics are primarily driven by the shape of the articulations with contributions from the surrounding soft tissues. The joint motion occurs about a single axis oriented medially and superiorly. Joint contact forces change during different stages of gait and are affected by hindfoot alignment and traumatic alterations to their normal anatomy. A valgus subtalar joint axis is likely a contributing, and perhaps primary, risk factor for progression to adult acquired flat foot. The subtalar joint axis also contributes to the clinical picture of a cavus foot and a special subset of patients with dynamic varus.