Tibial Nerve: Anatomy, Origin, Course, Branches, Relations, Function, Clinical Significance, MRI & CT Imaging

Topic

Tibial nerve

The tibial nerve is the larger terminal branch of the sciatic nerve, arising in the posterior thigh and extending into the foot. It carries both motor and sensory fibers and supplies most of the posterior compartment of the leg, the sole of the foot, and associated joints. It is a key component of the lumbosacral plexus and clinically significant due to its frequent involvement in trauma, entrapment syndromes, and neuropathies.

Synonyms

Internal popliteal nerve (historical)
Tibial division of sciatic nerve
Medial sciatic branch

Origin, Course, and Branches

Origin:
- Arises from the ventral divisions of L4–S3 nerve roots within the sciatic nerve in the pelvis
- Becomes distinct in the posterior thigh at the apex of the popliteal fossa when sciatic nerve divides into tibial and common peroneal nerves
Course:
- Descends vertically through the popliteal fossa, deep to gastrocnemius
- Passes between the heads of the gastrocnemius and beneath the soleus
- Runs with posterior tibial vessels in the deep posterior compartment
- Enters the foot by passing behind the medial malleolus through the tarsal tunnel (beneath the flexor retinaculum)
Branches:
- Muscular branches: Supply gastrocnemius, soleus, plantaris, popliteus, tibialis posterior, flexor digitorum longus, flexor hallucis longus
- Cutaneous branches: Sural nerve (via communicating branch), medial calcaneal branches
- Terminal branches: Medial and lateral plantar nerves in the foot

Relations

In popliteal fossa: Lies superficial to popliteal vessels, deep to fascia and fat
In leg: Descends with posterior tibial artery and vein, enclosed within neurovascular bundle
At ankle (tarsal tunnel): Lies beneath flexor retinaculum, posterior to medial malleolus, medial to posterior tibial artery
In foot: Divides into medial and lateral plantar nerves beneath abductor hallucis

Function

Motor: Innervates posterior leg muscles (plantarflexors and toe flexors), intrinsic muscles of sole of foot
Sensory: Provides sensation to posterolateral leg, heel, plantar surface of the foot, and toes
Reflex: Contributes to ankle (Achilles) reflex

Clinical Significance

Injured in knee dislocations, tibial fractures, or posterior compartment trauma
Entrapment syndromes: Tarsal tunnel syndrome (compression at medial malleolus)
Target for nerve blocks in anesthesia for foot and ankle surgery
Involved in polyneuropathies and radiculopathies affecting L4–S3 roots
Easily evaluated in musculoskeletal imaging for entrapment or compressive neuropathies

MRI Appearance

T1-weighted images:

Nerve appears as a linear low-to-intermediate signal structure
Surrounded by bright fat within the neurovascular bundle, enhancing visibility

T2-weighted images:

Nerve shows intermediate to mildly hyperintense signal compared to muscle
Pathology (neuritis, entrapment, trauma) shows bright hyperintensity

STIR (Short Tau Inversion Recovery):

Normal nerve: low signal
Pathologic nerve: hyperintense due to edema or inflammation

Proton Density Fat-Saturated (PD FS):

Nerve shows low-to-intermediate signal
Pathology: bright focal or diffuse hyperintensity (neuropathy, tear, entrapment)

T1 Fat-Sat Post-Contrast:

Normal nerve: minimal or no enhancement
Pathology: focal or diffuse enhancement (inflammatory neuropathy, tumor, or infection)

3D T2 SPACE / CISS:

Nerve shows intermediate to mildly hyperintense signal compared to muscle
Surrounded by bright fat or fluid, providing high-contrast delineation
Excellent for tracking nerve along its course and detecting compression

CT Appearance

Non-Contrast CT:

Nerve is not sharply visualized, seen only as small soft tissue density within posterior leg and tarsal tunnel fat planes
HRCT shows nerves as small tubular soft tissue densities

Post-Contrast CT:

Nerve itself shows little to no enhancement
Pathological processes (tumor, inflammatory infiltration, hematoma) may appear as enhancing or mass-like soft tissue surrounding the nerve

MRI image

CT image

MRI images

Topics