Tibialis posterior muscle

At a glance

English

Tibialis posterior muscle

Latin (TA2)

Musculus tibialis posterior

System

Muscle

Region

Lower limb

Side

Paired, left and right

About the tibialis posterior muscle

Tibialis posterior is the most deeply placed muscle of the posterior compartment of the leg, lying directly on the interosseous membrane between the tibia and fibula. It is covered by flexor digitorum longus medially, flexor hallucis longus laterally and soleus behind. Its tendon is a main support of the inner arch of the foot.

It arises from the back of the interosseous membrane and the adjacent posterior surfaces of the tibia, below the soleal line, and of the fibula. In the lower leg its tendon crosses beneath that of flexor digitorum longus and runs in a groove behind the medial malleolus, held by the flexor retinaculum. It then passes under the foot and fans out. The main part attaches to the tuberosity of the navicular. Other slips reach all three cuneiforms, the cuboid, the bases of the second to fourth metatarsals and the calcaneal sustentaculum tali.

The muscle inverts the foot and helps plantarflex the ankle. Its chief role, however, is to hold up the medial longitudinal arch and keep the hindfoot aligned while the foot bears weight, stiffening the midfoot so it can act as a lever at push-off. Its many attachments under the tarsal bones support the head of the talus from below. It is supplied by the tibial nerve and by the posterior tibial artery, with the fibular artery contributing.

Failure of this tendon is the commonest cause of flatfoot developing in adults. When the tendon becomes stretched, degenerate or torn, the arch gradually collapses and the heel drifts outwards because eversion is no longer opposed. Patients notice pain and swelling behind the medial malleolus and find it hard to rise onto the toes of the affected foot. An extra bone, the accessory navicular, sometimes forms within the tendon at its insertion and can become painful.

Attachments, action and supply

Origin

Posterior surface of the interosseous membrane and the adjoining posterior surfaces of the tibia and fibula.

Insertion

Tuberosity of the navicular, with slips to the cuneiforms, cuboid, bases of the second to fourth metatarsals and the sustentaculum tali.

Action

Inverts the foot, assists plantarflexion and supports the medial longitudinal arch.

Nerve supply

Tibial nerve (L4, L5).

Blood supply

Posterior tibial artery, with branches of the fibular artery.