Anatomy Atlas

Common fibular nerve

Nervus fibularis communis
Also: Common peroneal nerve · Peroneal nerve
NerveHigh-yielddraftNeuroMSK

Lateral terminal branch of the sciatic nerve that winds around the fibular neck — the most commonly injured nerve of the lower limb. Injury causes foot drop and numbness of the dorsum of the foot.

Core anatomy

Location

Lateral side of the popliteal fossa, then around the neck of the fibula into the leg.

Root values

L4–S2.

Origin

Sciatic nerve, at the apex of the popliteal fossa

Course

Follows the medial border of biceps femoris to the lateral side of the popliteal fossa, passes behind the fibular head, then winds around the fibular neck (superficial, against bone) and divides deep to fibularis longus into the superficial and deep fibular nerves.

Branches
  • Superficial fibular nerve: lateral compartment (fibularis longus and brevis → eversion); skin of the lower lateral leg and most of the dorsum of the foot
  • Deep fibular nerve: anterior compartment (tibialis anterior, extensor digitorum longus, extensor hallucis longus, fibularis tertius → dorsiflexion and toe extension) and extensor digitorum brevis; skin of the first web space
  • Lateral sural cutaneous nerve and the sural communicating branch; articular branches to the knee
Motor

The anterior and lateral compartments of the leg (dorsiflexion, toe extension, eversion) and short head of biceps femoris (via the sciatic division).

Sensory

Lateral leg, dorsum of the foot, and the first web space.

Relations

Palpable (and vulnerable) as it crosses the fibular neck just below the fibular head.

Other structures innervated

Found in

Mentioned in

Generated automatically from links in other entries.

Compartments of the leg (cross-section)Mid-leg cross-section. The tibia lies anteromedially and the fibula laterally, joined by the interosseous membrane. Anterior and posterior intermuscular septa and the transverse intermuscular septum divide the leg into anterior, lateral, deep posterior and superficial posterior compartments, each with its own nerve.TibiaFibulaGreat saphenous v.Small saphenous v. + sural n.Anterior ↑ · medial on the left (schematic)AnteriorTibialis anterior, EHL, EDL, fibularis tertiusDeep fibular n. · anterior tibial a.Dorsiflexion, toe extensionLateralFibularis longus and brevisSuperficial fibular n.EversionDeep posteriorTibialis posterior, FDL, FHLTibial n. · posterior tibial and fibular aa.Inversion, toe flexionSuperficial posteriorGastrocnemius, soleus, plantarisBranches of the tibial n.Plantarflexionnervearteryvein

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Compartments of the leg. Schematic mid-leg cross-section: four compartments separated by bone, the interosseous membrane and intermuscular septa, each with its own nerve. Compartment syndrome most often affects the anterior compartment.
Original schematic, created for this atlas.
Lower limb dermatomes (anterior view) and key musclesL1 over the groin and upper thigh; L2 the upper anterior thigh; L3 the lower anterior thigh and knee; L4 the medial leg and medial malleolus; L5 the lateral leg and dorsum of the foot including the great toe; S1 the lateral edge of the foot and little toe. Table: L2 hip flexion; L3 knee extension; L4 ankle dorsiflexion and patellar reflex; L5 great toe extension; S1 plantarflexion and ankle reflex.L1L2L3L4L5S1LateralMedial (great toe)ASIA key sensory point (S1: lateral heel)RootKey muscle actionReflexL2Hip flexion—L3Knee extension—L4Ankle dorsiflexionPatellar (L3–L4)L5Great toe extension—S1Ankle plantarflexionAnkle (Achilles)Foot drop with weak inversion → L5 root;with normal inversion → common fibular nerve.Maps differ between sources; neighbours overlap.

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Lower limb dermatomes and key muscles. Right lower limb, anterior view (medial = your right). Dots are ASIA key sensory points; the table gives the key muscle action and reflex for each root. Dermatome maps differ between sources.
Original schematic, created for this atlas.
Anterior leg dissection showing the common fibular nerve dividing into the deep fibular nerve (with the anterior tibial artery) and the superficial fibular nerve
Deep nerves of the front of the leg: common fibular nerve dividing into deep and superficial fibular nerves.
Henry Vandyke Carter, Gray's Anatomy of the Human Body, 20th ed. (1918), Fig. 835. Source · Public domain (Public domain in the US: published before January 1, 1931 (per Wikimedia Commons))

Clinical correlations

Common fibular neuropathy (foot drop) PANCE

Mechanism / lesion

Compression or trauma at the fibular neck — habitual leg crossing, prolonged squatting or kneeling, weight loss, tight casts or braces, bed rest; fibular neck fracture; knee dislocation or LCL injury.

Classic presentation

Foot drop (weak dorsiflexion and toe extension) with weak eversion, a high-stepping (steppage) gait, and numbness of the lateral leg and dorsum of the foot. Inversion (tibial nerve) and the ankle reflex are normal — which distinguishes it from an L5 radiculopathy (inversion and hip abduction also weak).

Anterior compartment syndrome PANCE

Mechanism / lesion

Raised pressure in the anterior compartment compresses the deep fibular nerve (see compartments of the leg).

Classic presentation

Severe pain, pain on passive toe flexion, and early numbness of the first web space.

High-yield PANCE pearls

  • Foot drop + weak eversion + dorsal foot numbness + normal inversion → common fibular nerve at the fibular neck.
  • Foot drop + weak inversion and hip abduction → L5 radiculopathy.
  • First web-space numbness = deep fibular nerve.
  • Leg crossing, tight cast or fibular neck fracture → fibular palsy.

Imaging anatomy

X-ray

Fibular neck fracture, knee dislocation.

MRI

Intraneural ganglion cysts from the proximal tibiofibular joint, masses; lumbar MRI if L5 radiculopathy is suspected.

Ultrasound

Shows compression or ganglion cysts at the fibular neck.

Physical exam

Surface landmarks

Palpable as a cord behind the fibular head and around the fibular neck.

Palpation

Tinel sign at the fibular neck.

Strength / function testing

Dorsiflexion and great toe extension (deep fibular), eversion (superficial fibular), inversion (tibial — preserved), hip abduction (L5 — preserved), ankle reflex (preserved). Sensation of the first web space and dorsum of the foot. Observe for steppage gait. EMG/nerve conduction studies localize the lesion.

Self-quiz

Q1.

After losing 20 kg, a woman who habitually sits with her legs crossed develops a right foot drop. Eversion is weak, inversion is normal, and the ankle reflex is intact. Sensation is reduced over the dorsum of the foot. Where is the lesion?

Show answer

C

Weight loss (less fat padding) and leg crossing compress the common fibular nerve at the fibular neck. Weak dorsiflexion and eversion with preserved inversion (tibial nerve) and a normal ankle reflex localize the lesion there rather than to L5.

Q2.

Sensory loss limited to the first web space between the great and second toes indicates injury to which nerve?

Show answer

B

The deep fibular nerve supplies only the skin of the first web space; the superficial fibular nerve supplies most of the dorsum of the foot.

Q3.

A patient has foot drop with weak ankle inversion and weak hip abduction. Where is the lesion most likely?

Show answer

C

Foot drop with weak inversion (tibialis posterior, tibial nerve) and weak hip abduction (gluteus medius, superior gluteal nerve) points to the L5 root, which feeds several nerves. A common fibular lesion spares inversion, and a sciatic lesion in the thigh spares the hip abductors.

Q4.

Which gait is typical of foot drop from common fibular nerve palsy?

Show answer

B

With weak dorsiflexion the toes drag, so the patient lifts the knee high to clear the foot: a high-stepping (steppage) gait. A Trendelenburg gait reflects hip abductor weakness.

Q5.

A patient has weak eversion of the foot and numbness over most of the dorsum of the foot, but dorsiflexion and toe extension are normal. Which nerve is injured?

Show answer

D

The superficial fibular nerve supplies the lateral compartment (fibularis longus and brevis → eversion) and the skin of most of the dorsum of the foot. The deep fibular nerve supplies the dorsiflexors and the first web space.

Flashcards

See also