The tibialis posterior muscle is a relatively small muscle located in 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 side. The muscle tendon runs down behind the medial malleolus and ends by segregating into main, plantar, and recurrent portions. The insertion of the main part takes place in the first cuneiform and the navicular tuberosity. The primary function of this muscle is to provide stability to the lower leg. It also facilitates foot inversion by its contraction and helps in the ankle's plantar flexion. 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 of flat foot in children and adults. The muscle's innervation takes place from the tibial nerve, and its arterial supply comes from the tibial artery. The interosseous membrane is also connected with this muscle, which attaches it to the fibula and tibia.