Tibialis posterior
Musculus tibialis posterior
Also known as: posterior tibialis, TP
The deepest muscle of the posterior compartment. It is the main invertor of the foot and the key dynamic support of the medial longitudinal arch.
Overview
Tibialis posterior arises from the interosseous membrane and the adjacent posterior surfaces of the tibia (below the soleal line) and fibula. Its tendon crosses behind the tibia beneath FDL and passes immediately behind the medial malleolus in its own compartment of the flexor retinaculum. It then spreads out on the sole. The main insertion is on the tuberosity of the navicular, with slips to all the cuneiforms, the cuboid, the sustentaculum tali and the bases of metatarsals 2–4.
It is the principal invertor of the foot and assists plantarflexion. By pulling up under the navicular and binding the tarsals together, it is the most important dynamic support of the medial longitudinal arch. It locks the midtarsal joints so that the foot becomes a rigid lever for push-off. It is supplied by the tibial nerve (L4–L5).
Anatomy
- Origin
Interosseous membrane and the posterior surfaces of the tibia (below the soleal line) and fibula.
- Insertion
Tuberosity of the navicular, with slips to the cuneiforms, cuboid, sustentaculum tali and the bases of metatarsals 2–4.
- Action
Inversion of the foot; plantarflexion of the ankle; support of the medial arch.
- Innervation
Tibial nerve.
- Nerve roots
L4–L5
- Arterial supply
Posterior tibial artery and fibular artery.
- Relations
Lies between FDL (medial) and FHL (lateral) in the deep compartment. Its tendon is the most anterior structure behind the medial malleolus.
Function
- Inverts the foot
- Plantarflexes the ankle
- Supports the medial longitudinal arch and stabilises the hindfoot
Clinical significance
Posterior tibial tendon dysfunction
Degeneration or rupture of the tendon, typically in middle-aged women with obesity or diabetes, is the commonest cause of acquired flatfoot in adults. Signs: the arch collapses, the heel goes into valgus, the patient cannot do a single-leg heel raise, and the "too many toes" sign is seen from behind.
Shin splints
Medial tibial stress syndrome (traction periostitis along the posteromedial tibial border) is linked to overuse of tibialis posterior, soleus and FDL in runners.
Mnemonics
Behind the medial malleolus
"Tom, Dick And Very Nervous Harry": Tibialis posterior, flexor Digitorum longus, Artery, Vein, Nerve (tibial), flexor Hallucis longus, from anterior to posterior.
Compiled from standard anatomy and physiology references — see the Muscular System sources. For education only; not medical advice.