The quadratus plantae muscle is a small, quadrilateral-shaped muscle located in the foot. It originates at the calcaneus (heel bone) and inserts into the tendon of the flexor digitorum longus muscle. The quadratus plantae muscle is located deep to the flexor digitorum longus muscle, and is one of several muscles that make up the posterior compartment of the foot.

The main function of the quadratus plantae muscle is to assist in flexion of the digits (toes) at the metatarsophalangeal joints (joints between the metatarsal bones and the phalanges of the toes). This movement is essential for activities such as gripping the ground with the toes, and helps to provide stability and balance when standing and walking. The quadratus plantae muscle also helps to flex the ankle joint, bringing the foot downwards. It is also used in activities that require stability and balance, such as standing on one foot or walking on uneven ground.