Fysiqal
Anatomy
Anatomy

Tibialis Posterior

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lower-legankletibialisdeep-posterior-compartment

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DefinitionA short reference note, not a full lesson.
Definition

The deep calf muscle that inverts the foot and is the primary dynamic support of the medial arch — the antagonist to the fibularis (peroneal) muscles.

Detail

The tibialis posterior lies deep to the soleus in the posterior compartment of the lower leg; its tendon passes behind the medial malleolus to insert broadly across the tarsal bones and metatarsals. Its primary action is inversion — rolling the sole of the foot inward, toward the midline — and it assists plantarflexion. It is the principal dynamic stabilizer of the medial longitudinal arch; dysfunction of this muscle/tendon is the leading cause of acquired flatfoot in adults.

Key facts

  • Action: inversion of the foot; assists plantarflexion.
  • Primary dynamic support of the medial longitudinal arch.
  • Antagonist to the fibularis longus/brevis (which evert the foot).
  • Tendon dysfunction is a leading cause of adult acquired flatfoot.

Connections

Sources

Cited in text — not yet linked
Not present in the original source corpus for this knowledge base (no source_pages). Added to close a taxonomy gap surfaced during the page-by-page foundations review: ankle eversion/inversion existed as valid motions with zero muscle attribution or exercises. Standard kinesiology fact, consistent with the Thompson structural-kinesiology terminology already used throughout this graph — flagged here as an explicit exception to this corpus's page-cited sourcing convention.

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Educational content only — not medical advice. Always consult a qualified professional for individualized guidance, especially around injury, pregnancy, or medical conditions.