Tibialis Posterior
Leg · Lower Limb
The tibialis posterior is the deepest muscle of the posterior compartment of the leg, lying centrally between the flexor digitorum longus and the flexor hallucis longus. It arises from the interosseous membrane and the adjacent posterior surfaces of the tibia and fibula, and its tendon passes behind the medial malleolus to fan out onto the navicular tuberosity, the cuneiforms, the cuboid, and the bases of the second to fourth metatarsals. From these medial and plantar attachments it inverts the foot and assists plantarflexion of the ankle, and its broad insertion makes it the key dynamic support of the medial longitudinal arch. It is supplied by the tibial nerve (L4, L5). Dysfunction of its tendon is a common cause of acquired flatfoot.
Origin, Insertion, Action & Nerve
Origin
Interosseous membrane, posterior surface of tibia, and posterior surface of fibula
Insertion
Navicular tuberosity, cuneiforms, cuboid, and bases of metatarsals 2–4
Action
Inversion of foot; plantarflexion of ankle; supports medial arch
Nerve
Tibial nerve (L4, L5)
Attachments explained
The Tibialis Posterior is defined first by where it attaches. Its origin is the more fixed anchor, usually the proximal or more stable end that stays put during contraction, while its insertion is the more mobile point that is pulled toward the origin when the muscle shortens.
Origin
Interosseous membrane, posterior surface of tibia, and posterior surface of fibula
Insertion
Navicular tuberosity, cuneiforms, cuboid, and bases of metatarsals 2–4
Action & function
When the Tibialis Posterior contracts, it produces the following movements: Inversion of foot; plantarflexion of ankle; supports medial arch.
As part of the Leg group of the Lower Limb, it works alongside neighbouring muscles to generate smooth, coordinated movement and to stabilise the structures it acts on.
Nerve supply & clinical relevance
The Tibialis Posterior receives its nerve supply from the Tibial nerve (L4, L5). This nerve carries fibres from spinal segment(s) L4, L5.
Because a muscle can only contract when its nerve is intact, injury to the Tibial nerve or to its spinal roots (L4, L5) can weaken or paralyse the Tibialis Posterior, impairing the movements it normally produces (inversion of foot). This is why knowing the innervation is central to localising nerve lesions in clinical practice.
How to study the Tibialis Posterior (the OIANS method)
Fix the tibialis posterior as the deep, central muscle of the calf whose tendon curls behind the medial malleolus, the most anterior of the three tendons passing there. Because it approaches the foot from the medial and plantar side, it inverts the foot and supports the medial arch, and its position deep to the other flexors explains why its attachments spread so widely across the tarsal and metatarsal bones.
Contrast it with the tibialis anterior: both invert the foot, but the posterior muscle is a plantarflexor from the back of the leg supplied by the tibial nerve, whereas the anterior muscle is a dorsiflexor from the front supplied by the deep fibular nerve. Anchor the clinical point that failure of the tibialis posterior tendon lets the medial arch collapse into flatfoot, which ties its arch-supporting action to a memorable consequence.
Frequently asked questions
Where is the Tibialis Posterior located?
The Tibialis Posterior is a muscle of the Leg group, located in the Lower Limb.
What is the origin of the Tibialis Posterior?
Interosseous membrane, posterior surface of tibia, and posterior surface of fibula
What is the insertion of the Tibialis Posterior?
Navicular tuberosity, cuneiforms, cuboid, and bases of metatarsals 2–4
What movements does the Tibialis Posterior produce?
Inversion of foot; plantarflexion of ankle; supports medial arch
What nerve supplies the Tibialis Posterior?
Tibial nerve (L4, L5)
Is the Tibialis Posterior free to study in OIANS?
The Tibialis Posterior is always free to browse. Its full origin, insertion, action and nerve details are open to everyone in the Muscle Directory. Quiz and Flashcard practice for the Lower Limb is part of the one-time Lifetime upgrade, though; only the Upper Limb decks are free to test yourself on.
Related muscles
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