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Tibialis Posterior — Individual Slips

tendines musculi tibialis posterioris (insertionis variae)

The tibialis posterior has the most complex foot insertion of any tendon, with slips to the navicular, all three cuneiforms, the cuboid, and three metatarsal bases. This broad fan-like attachment distributes arch support forces across the entire medial column and midfoot. PTTD typically tears the navicular slip first (the largest and most loaded component), while the accessory slips may remain intact and partially preserve arch height even in advanced stages.

Region: Foot & Ankle

Biomechanics

Function & Actions

The fan-like insertion distributes the medial arch support force across the entire midfoot; the primary navicular slip is the functional anchor; accessory slips maintain the transverse and longitudinal arch relationships

Clinical Relevance

Clinical Notes

MRI of PTTD shows signal abnormality and thinning of the primary navicular slip first, followed by progressive failure of the secondary slips. The accessory navicular (an accessory ossicle at the navicular tuberosity in 10-12% of the population) is the site of accessory navicular syndrome where the medial tibialis posterior slip avulses from the ossicle.

Pathology

Common Injuries & Conditions

Accessory Navicular Syndrome

Tibialis posterior medial slip avulsion or stress reaction at the accessory navicular producing medial foot pain managed with orthotics and surgical excision for refractory cases.