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Common fibular nerve

The common fibular (peroneal) nerve is one of the two terminal branches of the sciatic nerve, the other being the tibial nerve. It is the smaller branch and descends obliquely along the lateral side of the popliteal fossa before curving around the neck of the fibula, where it is vulnerable to injury. It supplies the muscles of the anterior and lateral compartments of the leg and provides sensory innervation to the dorsum of the foot and anterolateral leg.

It is clinically significant as compression or injury to this nerve commonly causes foot drop.

Synonyms

  • Common peroneal nerve

  • External popliteal nerve (historical)

  • Lateral division of the sciatic nerve

Origin, Course, Branches, and Termination

  • Origin:

    • Arises in the popliteal fossa as the lateral terminal branch of the sciatic nerve, at the level of the superior angle of the popliteal fossa.

  • Course:

    • Runs laterally along the medial border of the biceps femoris muscle

    • Descends obliquely across the lateral side of the popliteal fossa

    • Passes posterior and then lateral to the fibular head and neck

    • Winds around the fibular neck, lying subcutaneously (most vulnerable site)

  • Branches:

    • Cutaneous:

      • Lateral sural cutaneous nerve → supplies skin of lateral upper leg

      • Peroneal communicating branch → joins with tibial contribution to form sural nerve

    • Articular:

      • Genicular branches to knee joint capsule

    • Terminal branches:

      • Superficial fibular (peroneal) nerve → supplies muscles of lateral compartment and skin of dorsum of foot

      • Deep fibular (peroneal) nerve → supplies muscles of anterior compartment, extensor digitorum brevis, and skin between 1st and 2nd toes

  • Termination (Insertion):

    • Divides into superficial and deep fibular nerves at the fibular neck

Relations

  • Anteriorly: Lateral head of gastrocnemius, fibular head and neck

  • Posteriorly: Plantaris muscle, lateral sural vessels

  • Medially: Popliteal vein, tibial nerve (in popliteal fossa)

  • Laterally: Biceps femoris tendon

  • At fibular neck: Lies subcutaneously, closely related to bone — a common site of entrapment or injury

Function

  • Motor:

    • Via superficial fibular nerve: innervates fibularis longus and brevis (lateral compartment → eversion of foot)

    • Via deep fibular nerve: innervates tibialis anterior, extensor digitorum longus, extensor hallucis longus, peroneus tertius, and extensor digitorum brevis (anterior compartment → dorsiflexion of ankle, extension of toes)

  • Sensory:

    • Anterolateral leg, dorsum of foot, and first interdigital cleft

Clinical Significance

  • Foot drop: Common result of injury at fibular neck

  • Compression neuropathy: Due to casts, prolonged leg crossing, or trauma

  • Entrapment syndromes: May occur near fibular head or in anterior tarsal tunnel

  • Iatrogenic injury: During knee, fibular, or popliteal fossa surgeries

  • Electrodiagnostic studies and MRI: Used for evaluating peroneal neuropathies

MRI Appearance

T1-weighted images:

  • Nerve shows low-to-intermediate signal intensity

  • Surrounded by bright fat planes that improve visualization

T2-weighted images:

  • Nerve shows intermediate to mildly hyperintense signal compared to muscle

  • Pathological nerves appear more hyperintense and swollen

STIR (Short Tau Inversion Recovery):

  • Normal nerve: low signal

  • Pathological nerve (neuropathy, neuritis, compression): bright hyperintensity

Proton Density Fat-Saturated (PD FS):

  • Nerve shows low-to-intermediate baseline signal

  • Pathology (edema, injury) appears bright hyperintensity

T1 Fat-Sat Post-Contrast:

  • Normal nerve enhances minimally or not at all

  • Pathological nerve shows focal or diffuse enhancement (neuritis, tumor, entrapment)

3D T2 SPACE / CISS:

  • Nerve shows intermediate to mildly hyperintense signal compared to muscle

  • Surrounded by bright CSF or fat, providing excellent contrast

  • Useful for tracing the nerve around the fibular head and detecting entrapment

CT Appearance

Non-Contrast CT:

  • HRCT shows nerve as a small soft tissue density structure

  • Fat planes outline location; trauma may show bone displacement affecting nerve

Post-Contrast CT:

  • Nerve itself does not enhance

  • Pathology (tumor, inflammation, infiltration) may appear as soft tissue thickening or abnormal enhancement along nerve course

MRI image

Common fibular (peroneal) nerve axial cross sectional anatomy 3T MRI AI enhanced radiology anatomy image-img-00000-00000

MRI image

Common fibular (peroneal) nerve axial cross sectional anatomy 3T MRI AI enhanced radiology anatomy image-img-00000-00000_00001

MRI image

Common fibular (peroneal) nerve coronal cross sectional anatomy 3T MRI AI enhanced radiology anatomy image-img-00000-00000

MRI image

Common fibular nerve mri image

MRI image

Common fibular nerve

CT image

Common fibular (peroneal) nerve ct 1

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Common fibular (peroneal) nerve ct axial

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Common fibular (peroneal) nerve ct coronal