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Tibialis posterior tendon (medial slip)

The tibialis posterior tendon (TPT) is the main tendon of the tibialis posterior muscle, which divides near its insertion into slips that attach to multiple tarsal bones. The medial slip is one of the most clinically important divisions, inserting primarily into the navicular tuberosity and often extending to adjacent bones. It plays a central role in maintaining the medial longitudinal arch of the foot and in hindfoot inversion and stabilization.

Injury or dysfunction of the medial slip is a hallmark of posterior tibial tendon dysfunction (PTTD), the leading cause of acquired adult flatfoot deformity.

Synonyms

  • Medial slip of tibialis posterior tendon

  • Navicular slip of posterior tibial tendon

  • Main insertion of tibialis posterior

Origin, Course, and Insertion

  • Origin: Tibialis posterior muscle arises from posterior surfaces of the tibia, fibula, and interosseous membrane.

  • Course: The tendon runs posterior to the medial malleolus, within the tarsal tunnel, supported by the flexor retinaculum.

  • Insertion (medial slip): Inserts strongly into the navicular tuberosity, sometimes with expansions to the medial cuneiform and first metatarsal base.

Tendon Attachments

  • Medial slip: Navicular tuberosity (primary attachment) ± medial cuneiform and base of 1st metatarsal

  • Central slip: Intermediate cuneiform and 2nd–4th metatarsal bases

  • Lateral slips: Cuboid and lateral cuneiform

Relations

  • Superiorly: Flexor digitorum longus tendon (crosses superficially)

  • Inferiorly: Navicular and spring ligament complex

  • Anteriorly: Talus and subtalar joint capsule

  • Posteriorly: Medial malleolus and tibia

  • Laterally: Other tibialis posterior tendon slips toward midfoot bones

Function

  • Arch support: Main dynamic stabilizer of the medial longitudinal arch

  • Foot inversion: Acts with tibialis anterior to invert the foot

  • Plantarflexion assistance: Aids gastrocnemius–soleus complex in plantarflexion

  • Hindfoot stability: Prevents valgus collapse of hindfoot during gait

Clinical Significance

  • Posterior tibial tendon dysfunction (PTTD): Most common pathology, leading to acquired flatfoot

  • Tears/ruptures: Medial slip tears cause progressive arch collapse and hindfoot valgus

  • Degeneration: Chronic tendinopathy common in middle-aged and elderly patients

  • Trauma: Acute ruptures may follow ankle injuries

  • Symptoms: Medial ankle pain, swelling, progressive flatfoot deformity

  • Surgical relevance: Reconstruction or tendon transfer may be required in severe cases

MRI Appearance

  • T1-weighted images:

    • Normal medial slip tendon: low signal intensity (dark band) along navicular

    • Muscle belly: intermediate signal

    • Pathology: tendinosis shows thickened tendon with intermediate signal intensity; partial tear = focal bright cleft

  • T2-weighted images:

    • Normal tendon: very low signal

    • Normal muscle: intermediate, slightly darker than T1

    • Tears or tendinosis: bright hyperintense signal within tendon fibers

    • Peritendinous fluid or spring ligament injury also appears hyperintense

  • STIR:

    • Normal tendon: dark

    • Pathology: hyperintense tendon thickening, edema, or peritendinous fluid

    • Useful in detecting subtle tenosynovitis and partial tears

  • Proton Density Fat-Saturated (PD FS):

    • Normal tendon: homogeneous dark structure

    • Pathology: bright intratendinous signal with surrounding peritendinous hyperintensity

    • Excellent for identifying partial-thickness tears of medial slip

  • T1 Fat-Sat Post-Contrast:

    • Normal: minimal enhancement

    • Tendinitis or synovitis: enhancement of tendon sheath

    • Chronic degenerative tendon with scar tissue shows peripheral enhancement

CT Appearance

Non-Contrast CT:

  • Tendon not well visualized; appears as soft tissue density along medial malleolus and navicular

  • Chronic tendinopathy may show calcification at navicular insertion

  • Bony deformity in advanced PTTD: navicular subluxation, arch collapse

Post-Contrast CT (standard):

  • Tendon sheath may enhance in inflammatory states

  • Useful for excluding bony pathology contributing to dysfunction

MRI image

Tibialis posterior tendon (medial slip) axial cross sectional anatomy 3T MRI AI enhanced radiology image-img-00000-00000

MRI image

Tibialis posterior tendon (medial slip) axial cross sectional anatomy 3T MRI AI enhanced radiology image-img-00000-00000_00001