Name

# Tibialis Posterior

Pronunciation

(tib-e-A-lus pos-TEER-i-or)

Origin/Proximal Attachment

Medial process arises from the posterior surface of the interosseous membrane, except at its most distal part, & from a lateral area on the posterior surface of the tibia between the soleal line above & the junction of the middle & lower thirds of the shaft below

Lateral part arises from a medial strip of the posterior fibula surface in its upper two 3rds

deep transverse

intermuscular septa that separate it from adjacent muscles

Insertion/Distal Attachment

more superficial, larger division, a direct continuation of the tendon, is attached to the navicular tuberosity, from which fibres continue to the inferior surface of the medial cuniform

a tendinous band passes laterally and a little proximally to the tip & distal margin of the sustentaculum tali of the calcaneus

the deeper lateral division gives rise to the tendon of origin of the medial limb of flexor hallucis brevis, & then continues between this muscle & the navicular & medial cuneiform bones to end on the intermediate cuneiform and the bases of the 2nd, 3rd & 4th metatarsals, the slip to the 4th metatarsal being the strongest

slips to the cuboid & lateral cuneiform have also been described

Action/Relevance

Stabilizes ankle joint

Adducts & inverts foot

Weakly plantar-flexes foot

it is the principal invertor of the foot

it may assist in vigorous plantar flexion

Innervation

Tibial nerve (L5, S1)

Notes

deepest of the flexor group

at is origin it lies between flexor hallucis longus & flexor digitorum longus, & is overlapped by both, but especially the former

proximal attachment consists of 2 pointed processes, separated by an angular interval which is traversed by the anterior tibial vessels

in the distal ¼ of the leg its tendon passes deep to that of flexor digitorum longus, with which it shares a groove behind the medial malleolus, each enclosed in a separate synovial sheath

it spans deep to the flexor retinaculum & superficial to the deltoid ligament to enter the foot

in the foot it is first inferior to the plantar calcanevicular ligament, where it contains a sesamoid fibrocartilage

the tendon then divides into two