Medial Calcaneal Nerve ( posterior cutaneous branches): Anatomy & MRI-CT Imaging

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Medial calcaneal nerve (posterior cutaneous branches)

The posterior cutaneous branches of the medial calcaneal nerve are small sensory branches that arise from the medial calcaneal nerve, itself a branch of the tibial nerve in the tarsal tunnel. These posterior branches supply the posteromedial aspect of the heel and proximal plantar skin, contributing to sensory innervation of the heel pad and surrounding cutaneous tissue.

They pierce the flexor retinaculum or emerge from the tarsal tunnel, coursing inferiorly and posteriorly across the medial side of the heel to reach the subcutaneous tissue. These small branches form a neural network supplying the heel’s posterior and inferior skin, often overlapping with terminal fibers of the lateral plantar and sural nerves.

Synonyms

Posterior heel branches of the medial calcaneal nerve
Cutaneous heel branches of tibial nerve
Posterior plantar cutaneous branches

Origin and Course

Origin: Arises from the medial calcaneal nerve, which branches from the tibial nerve near or within the tarsal tunnel, posterior to the medial malleolus.
Course: The posterior cutaneous branches pierce the flexor retinaculum or travel beneath it, descending toward the posterior heel region. They pass superficial to the calcaneal tuberosity, running within the subcutaneous layer, and terminate in the posterior heel pad skin.

Relations

Superiorly: Flexor retinaculum and tendons of the deep posterior compartment
Inferiorly: Calcaneal fat pad and plantar fascia
Anteriorly: Abductor hallucis and quadratus plantae muscles (deep plane)
Posteriorly: Skin and subcutaneous tissue of the heel
Laterally: Terminal twigs of the sural nerve
Medially: Branches of the medial plantar nerve and small vessels near the medial malleolus

Function

Sensory innervation: Provides cutaneous sensation to the posteromedial and inferior heel region
Protective feedback: Contributes to tactile and pressure sensation of the heel during stance phase
Clinical importance: Injury or entrapment causes heel dysesthesia, burning pain, or numbness, commonly part of tarsal tunnel syndrome

Clinical Significance

Entrapment neuropathy: Can occur within the tarsal tunnel or due to fibrotic changes near the flexor retinaculum
Heel pain syndrome: Involvement leads to medial heel pain, often misdiagnosed as plantar fasciitis
Surgical relevance: At risk during medial ankle or heel procedures (tarsal tunnel decompression, calcaneal osteotomy)
Iatrogenic injury: May occur after heel spur or plantar fascia surgery, leading to sensory loss or neuropathic pain
Diagnostic relevance: MRI and high-resolution ultrasound help localize nerve thickening, edema, or entrapment

MRI Appearance

T1-weighted images:
- Posterior cutaneous branches appear as thin, low-to-intermediate signal linear structures in the posteromedial ankle and heel fat.
- Surrounded by bright subcutaneous fat, providing contrast for identification.
- Nerve thickening or neuroma appears as focal fusiform intermediate-signal mass.
T2-weighted images:
- Normal branches: low-to-intermediate signal relative to muscle, darker than on T1.
- Neuropathy or entrapment: hyperintense signal with focal swelling or irregularity.
- Adjacent fat stranding or fascial edema may be present in chronic compression.
STIR (Short Tau Inversion Recovery):
- Normal: low signal intensity against bright fat background.
- Pathology: hyperintense signal along the course of the nerve or near the flexor retinaculum, indicating neuritis or edema.
Proton Density Fat-Saturated (PD FS):
- Normal nerve: low-to-intermediate signal linear band.
- Pathology: focal or diffuse bright hyperintensity within the nerve, often extending proximally into the tarsal tunnel.
- Excellent for detecting subtle neuritis, fibrosis, or post-surgical changes.
T1 Fat-Sat Post-Contrast:
- Normal: minimal or no enhancement.
- Pathologic nerves: enhancing thickened segments at the point of entrapment.
- Surrounding perineural enhancement may suggest inflammatory neuritis or post-traumatic fibrosis.

CT Appearance

Non-Contrast CT:

Nerves not directly visualized; appear as fine soft tissue strands in heel fat.
Indirect indicators of pathology include fat stranding, soft tissue swelling, or post-traumatic fibrosis.
Bony abnormalities (heel spurs, osteophytes, or callus formation) may cause nerve impingement.

MRI image

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