Origin and Course
The tibial nerve (n. tibialis) travels through the popliteal fossa and posterior leg, dividing into its two terminal branches—the medial and lateral plantar nerves—posterior to the medial malleolus.
The anatomical landmark for this bifurcation is the space between the tibialis posterior (m. tibialis posterior) and flexor digitorum longus (m. flexor digitorum longus) muscles, where the tibial nerve transitions into the medial and lateral plantar nerves.
From here, the medial and lateral plantar neurovascular bundles enter the tarsal tunnel (canalis calcaneus) to reach the sole of the foot. Within the sole, the medial plantar vessels and nerve (a., v., n. plantares mediales) travel in the medial intermuscular septum.
Topography and Relations
In the medial retromalleolar region, key structures include the tibial nerve (n. tibialis), medial plantar nerve (n. plantaris medialis), lateral plantar nerve (n. plantaris lateralis), posterior tibial artery (a. tibialis posterior), flexor retinaculum (retinaculum mm. flexorum), calcanean branches of the tibial neurovascular bundle, and the synovial sheaths and tendons of the flexor digitorum longus, tibialis posterior, and flexor hallucis longus muscles.
In the deep layer of the sole, anatomical structures include the medial plantar artery and nerve (a., n. plantaris medialis), the tendon of the flexor digitorum longus (tendo m. flexoris digitorum longi), and the quadratus plantae muscle (m. quadratus plantae).
Muscle Innervation
The medial plantar nerve innervates muscles of the great toe, the flexor digitorum brevis, and the lumbricals.
- Flexor digitorum brevis (m. flexor digitorum brevis) — flexes the middle phalanges of digits II–V and supports the longitudinal arch of the foot.
- Abductor hallucis (m. abductor hallucis) — abducts and flexes the proximal phalanx of the great toe and supports the medial arch.
- Flexor hallucis brevis (m. flexor hallucis brevis) — the medial part is innervated by the n. plantaris medialis; flexes the proximal phalanx of the great toe.
- Lumbricals (mm. lumbricales) — the first lumbrical is typically innervated by the medial plantar nerve (along with contributions to the medial two lumbricals).
Cutaneous Innervation
The medial plantar nerve supplies sensory innervation to the skin of the medial part of the sole, the medial margin, and the central sole.
It gives rise to common plantar digital nerves (nn. digitales plantares communes) and proper plantar digital nerves (nn. digitales plantares proprii). The cutaneous innervation zone covers the skin of digits I, II, III, and the medial half of digit IV.