Common Fibular Nerve: Course, Branches and Foot Drop

By Dr Richard Miller, MBChB FRCS · Reviewed 1 October 2026

The common fibular nerve is the smaller terminal branch of the sciatic nerve, running along the lateral side of the popliteal fossa and around the neck of the fibula. It carries L4–S2 fibres and divides into the superficial and deep fibular nerves, which supply the lateral and anterior compartments of the leg and most of the dorsum of the foot.

Common Fibular Nerve · key facts

Roots: L4–S2, posterior divisions (common fibular part of the sciatic nerve)
Course: Medial edge of biceps femoris, behind the fibular head, around the fibular neck
Motor supply: Lateral compartment (superficial branch) and anterior compartment and extensor digitorum brevis (deep branch)
Sensory supply: Upper lateral leg, lower anterolateral leg, dorsum of foot
Branches: Lateral sural cutaneous, sural communicating, articular, superficial and deep fibular nerves
Key relations: Subcutaneous at the fibular neck, deep to fibularis longus
Injury: Foot drop, loss of eversion, numb dorsum of foot; inversion spared

Course

The common fibular (peroneal) nerve runs from the apex of the popliteal fossa to the neck of the fibula, where it divides; its whole course is only a few centimetres long.

In the popliteal fossa

It arises where the sciatic nerve divides, usually at the apex of the fossa, and follows the medial border of biceps femoris and its tendon down the lateral side of the fossa. It passes over the back of the lateral head of gastrocnemius.

At the fibula

The nerve passes behind the head of the fibula and then winds forward around the lateral side of the fibular neck, lying directly on bone under only skin and fascia. It enters the substance of fibularis longus, and between that muscle and the fibular neck it divides into its superficial and deep branches.

Branches and distribution

The common fibular nerve gives cutaneous and articular branches in the popliteal fossa and then ends as the superficial and deep fibular nerves.

Branch	Motor	Sensory
Lateral sural cutaneous nerve	None	Skin of the upper lateral leg
Sural communicating branch	None	Joins the medial sural cutaneous nerve to form the sural nerve (variable)
Articular branches	None	Knee (with the lateral genicular arteries) and the superior tibiofibular joint (recurrent articular branch)
Superficial fibular nerve	Fibularis longus, fibularis brevis	Lower anterolateral leg and most of the dorsum of the foot and toes
Deep fibular nerve	Tibialis anterior, extensor hallucis longus, extensor digitorum longus, fibularis tertius, extensor digitorum brevis, extensor hallucis brevis	First web space

Superficial fibular nerve

The superficial fibular nerve descends in the lateral compartment between the fibular muscles and extensor digitorum longus. It pierces the deep fascia in the lower third of the leg on its anterolateral surface and divides into medial and intermediate dorsal cutaneous nerves. These supply the dorsum of the foot, except the first web space (deep fibular nerve) and the lateral border (sural nerve).

The short head of biceps femoris is supplied by the common fibular part of the sciatic nerve in the thigh, before the common fibular nerve proper begins.

Relations

The defining relation of the common fibular nerve is the fibular neck, where it lies on bone just beneath the skin and is the most exposed nerve in the lower limb.

Popliteal fossa: biceps femoris tendon laterally, lateral head of gastrocnemius deep, tibial nerve diverging medially.
Fibular head and neck: skin and deep fascia superficially, bone deep, fibularis longus wrapping around it as it divides.
Surface marking: the nerve can be rolled under the finger just below and behind the palpable head of the fibula.

Clinical relevance

The common fibular nerve is the most frequently injured nerve in the lower limb, and its injury causes foot drop.

Causes

External pressure: tight plaster casts or splints, prolonged leg crossing, squatting, poorly padded stirrups in the lithotomy position, and pressure in bedbound or anaesthetised patients.
Fibular neck fracture and direct blows to the lateral knee.
Knee dislocation and posterolateral corner injuries, which stretch the nerve.
Weight loss, which removes the fat that normally cushions the nerve.
Ganglion cysts arising from the superior tibiofibular joint.

Signs

The foot hangs in plantarflexion and inversion. The patient walks with a high-stepping (steppage) gait so the toes clear the ground, and the foot slaps down on heel strike. Dorsiflexion of the ankle and toes and eversion are weak, and sensation is lost over the lower lateral leg and the dorsum of the foot.

Distinguishing it from an L5 root lesion

A common fibular nerve palsy spares inversion, because tibialis posterior is supplied by the tibial nerve, and spares hip abduction, supplied by the superior gluteal nerve. An L5 radiculopathy weakens both, since tibialis posterior and gluteus medius share the L5 root. The ankle jerk is preserved in both.

How it is examined

On a cadaveric spotter, in an OSPE and in MRCS Part B anatomy.

A pin on the nerve running along the medial edge of the biceps femoris tendon in the lateral popliteal fossa is the common fibular nerve; the midline nerve is the tibial nerve.
On a leg prosection, a nerve wrapping around the lateral side of the fibular neck under fibularis longus is the common fibular nerve at its point of division.
Classic viva: the patient has foot drop after a below-knee cast. Name the nerve, the site of compression and the deficit, then explain how to tell it from an L5 root lesion (test inversion and hip abduction).
Know the sensory map of the dorsum of the foot: first web space deep fibular, lateral border sural, the rest superficial fibular.
Expect to be asked which hamstring is supplied by the common fibular part of the sciatic nerve: the short head of biceps femoris.

Key points

The common fibular nerve (L4–S2) is the smaller terminal branch of the sciatic nerve.
It follows biceps femoris out of the popliteal fossa and winds around the fibular neck.
It divides into the superficial fibular nerve (lateral compartment) and the deep fibular nerve (anterior compartment).
It is the most commonly injured nerve in the lower limb, usually at the fibular neck.
Injury causes foot drop and loss of eversion, with inversion preserved.

Common questions

What does the common fibular nerve supply?

Through its two terminal branches the common fibular nerve supplies all the muscles of the anterior and lateral compartments of the leg, plus extensor digitorum brevis and extensor hallucis brevis on the dorsum of the foot. It therefore dorsiflexes the ankle, extends the toes and everts the foot. Its skin territory is the lateral leg and most of the dorsum of the foot.

Why does common fibular nerve injury cause foot drop?

Common fibular nerve injury paralyses tibialis anterior and the long toe extensors, the only muscles that dorsiflex the ankle. Without them the foot hangs in plantarflexion as the leg swings forward, so the toes catch the ground. Patients compensate by lifting the knee high, a steppage gait, and the foot slaps down at each step. The fibular muscles are also weak, so eversion is lost.

Where is the common fibular nerve most easily damaged?

The common fibular nerve is most easily damaged where it winds around the neck of the fibula, just below the lateral side of the knee. Here it lies directly on bone with only skin and fascia over it, so it is compressed by plaster casts, leg crossing, stirrups and prolonged bed rest, and torn by fibular neck fractures and knee dislocations.

References

Gray's Anatomy: The Anatomical Basis of Clinical Practice. Standring S (ed). Elsevier. 42nd edition, 2020.
Moore's Clinically Oriented Anatomy. Moore KL, Dalley AF, Agur AMR. Wolters Kluwer. 9th edition, 2022.
Last's Anatomy: Regional and Applied. Elsevier.