The tibialis posterior muscle is a relatively small muscle located within the back side of the calf. It is also the most centrally located muscle in the leg, arising from the inner borders of the fibula and tibia on the posterior (rear) side. The muscle’s tendon runs down behind the medial malleolus (bony protrusion on the inside of the ankle) and ends by segregating into the main, plantar, and recurrent portions.

The primary function of this muscle is to provide stability to the lower leg. It also facilitates foot inversion (swiveling inward) and aids the ankle’s plantar flexion (flexing the foot or toes downward). Additionally, the muscle performs a key role in providing support to the foot’s medial arch. Any dysfunction of the tibialis posterior muscle may result in a condition known as ‘flat foot syndrome’ in children and adults.

The tibial nerve innervates the muscle, and its blood supply comes from the tibial artery.