Quadratus plantae is one of the muscles of the intermediate layer of the sole of the foot. It arises from the medial and lateral sides of the calcaneus. It runs anteriorly to insert into the tendon of flexor digitorum longus.
Quadratus plantae acts to assist flexor digitorum longus in flexion of the lateral four toes. Its main advantage is assistance when the ankle is plantar flexed.
It is innervated by the lateral plantar nerve (S2,3).