**3. Biomechanics**

The calcaneus provides important static and dynamic functions of the foot and ankle. At rest, the static arch of the foot places 60% of weight-bearing stress on the plantar aponeurosis [18]. The plantar aponeurosis can absorb more stress as it becomes tauter, known as the windlass effect [19]. The windlass effect is essentially the tightening of the plantar fascia with dorsiflexion of the metatarsophalangeal joint, which elevates the medial longitudinal arch. The calcaneus's shape allows the plantar aponeurosis to change tension without collapsing the lateral or medial longitudinal arches [19]. The calcaneus dynamically supports movement and function with inversion and eversion through the subtalar joint, forming a rigid lever arm during toe-off and accommodating heel strike [20].
