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Tibialis posterior muscle

The tibialis posterior (TP) is the deepest and most central muscle of the posterior compartment of the leg. It plays a key role in foot inversion, arch support, and plantarflexion assistance. The tibialis posterior tendon (PTT) is clinically significant as it runs posterior to the medial malleolus within the tarsal tunnel, where it is prone to tendinopathy and rupture. Dysfunction of the PTT is a leading cause of acquired adult flatfoot deformity.

Synonyms

  • Posterior tibial muscle

  • Tibialis posticus

Origin, Course, and Insertion

  • Origin: Posterior surfaces of tibia and fibula, and the interosseous membrane

  • Course: Muscle fibers converge into a tendon that passes behind the medial malleolus, deep to the flexor retinaculum, within the tarsal tunnel

  • Insertion: Primarily on the navicular tuberosity, with slips to the cuneiforms, cuboid, and bases of the 2nd–4th metatarsals

Tendon Attachments

  • Runs posterior to the medial malleolus as the most anterior tendon in the order Tom, Dick, And Very Nervous Harry (Tibialis posterior, Flexor digitorum longus, posterior tibial Artery/Vein, tibial Nerve, Flexor hallucis longus)

  • Inserts mainly on the navicular, with expansions to the midfoot bones, stabilizing the medial arch

Relations

  • Superiorly: Soleus and flexor digitorum longus

  • Inferiorly: Medial tarsal bones and plantar ligaments

  • Medially: Skin and flexor retinaculum

  • Laterally: Flexor hallucis longus and fibula

  • Posteriorly: Tibia and interosseous membrane

Nerve Supply

  • Tibial nerve (L4–L5)

Arterial Supply

  • Posterior tibial artery and branches

  • Additional supply from fibular (peroneal) artery branches

Venous Drainage

  • Posterior tibial veins, draining into the popliteal vein

Function

  • Foot inversion: Primary inverter of the foot

  • Arch support: Maintains medial longitudinal arch integrity

  • Plantarflexion: Assists gastrocnemius and soleus in plantarflexion at the ankle

  • Dynamic stabilizer: Essential for gait, particularly push-off phase

Clinical Significance

  • Posterior tibial tendon dysfunction (PTTD): Leads to progressive flatfoot deformity

  • Tendon tears/ruptures: May cause medial ankle pain and loss of inversion strength

  • Tarsal tunnel syndrome: Compression of tibial nerve may coexist with tendon pathology

  • Imaging importance: MRI best for tendon tears, degeneration, and tenosynovitis

MRI Appearance

  • T1-weighted images:

    • Normal muscle: intermediate signal

    • Normal tendon: low signal (dark band) posterior to medial malleolus

    • Tendinopathy: tendon thickening with intermediate-to-bright intratendinous signal

    • Tears: discontinuity with surrounding bright fluid

  • T2-weighted images:

    • Normal muscle: intermediate-to-dark signal (slightly darker than on T1)

    • Normal tendon: uniformly low signal

    • Tendinopathy: bright intratendinous foci or diffuse hyperintensity

    • Partial tears: irregular bright signal extending to surface

    • Complete tears: tendon gap with surrounding hyperintense fluid

  • STIR:

    • Normal muscle: intermediate-to-dark

    • Pathology: bright hyperintense signal in tendon sheath or surrounding soft tissues, indicating edema or tenosynovitis

  • Proton Density Fat-Saturated (PD FS):

    • Normal tendon: uniformly dark

    • Pathology: bright signal abnormalities in tendon fibers, excellent for detecting partial-thickness tears

    • Normal muscle: intermediate-to-dark, pathology shows focal bright areas in degeneration or edema

  • T1 Fat-Sat Post-Contrast:

    • Normal tendon: minimal enhancement

    • Tendinopathy/tenosynovitis: diffuse enhancement of tendon sheath

    • Partial tears: peripheral enhancement with central gap

    • Complete ruptures: tendon discontinuity with enhancing granulation tissue at margins

CT Appearance

Non-Contrast CT:

  • Muscle: soft-tissue density, not well differentiated

  • Tendon: fine dense band posterior to medial malleolus

  • Chronic tendinopathy: tendon thickening or calcific deposits

Post-Contrast CT (standard):

  • Muscle enhances uniformly

  • Pathology: inflamed tendon sheath may show enhancement

  • Less sensitive than MRI but useful in cases of tendon calcification or bony enthesopathy

MRI image

Tibialis posterior muscle axial cross sectional anatomy 3T MRI AI enhanced radiology image-img-00000-00000

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Tibialis posterior muscle axial cross sectional anatomy 3T MRI AI enhanced radiology image-img-00000-00000_00001

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Tibialis posterior muscle axial cross sectional anatomy 3T MRI AI enhanced radiology image-img-00000-00000_00002

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Tibialis posterior muscle axial cross sectional anatomy 3T MRI AI enhanced radiology image-img-00000-00000_00003

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Tibialis posterior muscle coronal cross sectional anatomy 3T MRI AI enhanced radiology image-img-00000-00000

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Tibialis posterior muscle 1

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Tibialis posterior muscle ct axial

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Tibialis posterior muscle ct coronal