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Medial plantar nerve

The medial plantar nerve is the larger terminal branch of the tibial nerve, supplying motor and sensory innervation to the medial plantar aspect of the foot. It is the main sensory nerve for the medial three and a half toes and motor nerve for several intrinsic foot muscles.

Anatomically, it is comparable to the median nerve in the hand — responsible for fine motor control and cutaneous sensation in the medial plantar region. Due to its superficial course in the sole, the nerve is vulnerable to compression, entrapment, trauma, and repetitive stress, especially in athletes and runners.

Synonyms

  • Internal plantar nerve

  • Medial terminal branch of tibial nerve

Origin, Course, and Insertion

  • Origin: Arises beneath the flexor retinaculum as the larger terminal branch of the tibial nerve, deep to the abductor hallucis muscle

  • Course:

    • Passes anteriorly between the abductor hallucis and flexor digitorum brevis muscles

    • Travels with the medial plantar artery in the medial compartment of the sole

    • Divides into digital branches supplying the medial sole and toes

  • Termination: Ends by dividing into common and proper plantar digital nerves that supply the medial three and a half toes

Relations

  • Superiorly: Flexor hallucis longus tendon and medial malleolus (at tarsal tunnel)

  • Inferiorly: Plantar aponeurosis and skin of the sole

  • Medially: Abductor hallucis muscle

  • Laterally: Flexor digitorum brevis muscle

  • Posteriorly: Tibial nerve bifurcation

  • Anteriorly: Digital branches to toes and skin

Function

  • Motor: Supplies abductor hallucis, flexor hallucis brevis, flexor digitorum brevis, and first lumbrical muscle

  • Sensory: Innervates skin of the medial three and a half toes and medial plantar surface of the sole

  • Proprioception: Provides sensory feedback aiding foot posture and balance

  • Clinical role: Key for toe flexion, balance, and medial arch control

Clinical Significance

  • Medial plantar neuropathy (Jogger’s foot): Compression of the nerve beneath the abductor hallucis fascia, causing burning pain and numbness along the medial sole

  • Entrapment: Often occurs between the abductor hallucis and navicular tuberosity or under tight footwear

  • Iatrogenic injury: Possible during plantar surgery or tibial nerve decompression

  • Symptoms: Burning pain, tingling, paresthesia over the medial sole and toes, worse during walking or running

  • Imaging relevance: MRI and CT help evaluate entrapment, neuropathy, mass lesions, or traumatic injuries affecting the nerve

MRI Appearance

  • T1-weighted images:

    • Normal nerve: intermediate signal intensity, visible as a slender tubular structure in the medial foot compartment

    • Surrounded by bright subcutaneous fat, aiding visualization

    • Chronic neuropathy: atrophy and fatty infiltration of supplied muscles (abductor hallucis, flexor hallucis brevis) appear as high signal areas on T1

  • T2-weighted images:

    • Normal nerve: darker than T1, intermediate-to-low signal

    • Entrapment or neuritis: focal or diffuse hyperintense signal within the nerve

    • Perineural edema and surrounding fascial thickening are common findings in chronic compression

  • STIR:

    • Normal nerve: dark to intermediate signal

    • Pathology: bright hyperintense signal indicates edema or inflammation

    • Particularly helpful in detecting subtle neuropathy, fascial entrapment, or neuritis

  • Proton Density Fat-Saturated (PD FS):

    • Normal: low-to-intermediate signal

    • Neuropathy: bright signal with or without perineural fluid

    • Useful for assessing adjacent muscle denervation edema and soft-tissue inflammation

  • T1 Fat-Sat Post-Contrast:

    • Normal: minimal or no enhancement

    • Pathologic nerve: patchy or linear enhancement due to neuritis, fibrosis, or perineural inflammation

    • Postoperative scar enhancement may simulate pathology but typically follows a different distribution

CT Appearance

Non-Contrast CT:

  • Nerve itself poorly visualized due to small caliber and soft-tissue density

  • Indirect signs: soft-tissue swelling, fascial thickening, or adjacent mass compressing the tarsal tunnel region

  • Chronic neuropathy: atrophy of intrinsic foot muscles or fatty infiltration visible in plantar compartments

Post-Contrast CT (standard):

  • Nerve not directly enhanced

  • Enhancing soft-tissue mass or inflammatory lesion may indicate cause of compression (ganglion cyst, tenosynovitis, or fibrosis)

  • Can help assess tarsal tunnel anatomy and surgical planning

MRI image

Medial plantar nerve axial cross sectional anatomy 3T MRI AI enhanced radiology image-img-00000-00000

MRI image

Medial plantar nerve axial cross sectional anatomy 3T MRI AI enhanced radiology image-img-00000-00000_00001

MRI image

Medial plantar nerve axial cross sectional anatomy 3T MRI AI enhanced radiology image-img-00000-00000_00002

MRI image

Medial plantar nerve axial cross sectional anatomy 3T MRI AI enhanced radiology image-img-00000-00000_00003

MRI image

Medial plantar nerve sag cross sectional anatomy 3T MRI AI enhanced radiology image-img-00000-00000