Common fibular nerve
Nervus fibularis communis
Also known as: common peroneal nerve, lateral popliteal nerve
The smaller terminal branch of the sciatic nerve (L4–S2). It winds superficially around the neck of the fibula and divides into the superficial and deep fibular nerves. It is the most commonly injured nerve of the lower limb, and the classic result is foot drop.
Overview
The common fibular nerve leaves the sciatic nerve at the apex of the popliteal fossa. It follows the medial border of biceps femoris to the lateral side of the fossa, passing over the lateral head of gastrocnemius. It then winds around the neck of the fibula, where it is subcutaneous, palpable and lies directly on bone. Here it passes deep to fibularis longus and divides into the superficial fibular nerve and the deep fibular nerve.
Before dividing it gives:
• the lateral sural cutaneous nerve, to the skin of the upper lateral leg;
• the sural communicating branch, which joins the medial sural cutaneous nerve from the tibial nerve;
• articular branches to the knee.
Its superficial position against the fibular neck makes it the most frequently injured nerve of the lower limb. Fractures, tight casts and external pressure can all damage it.
- Location
Lateral popliteal fossa (along biceps femoris) → around the neck of the fibula → divides within fibularis longus.
Anatomy
- Innervation
Through its branches:
• the anterior compartment of the leg (dorsiflexors and toe extensors; deep fibular);
• the lateral compartment (evertors; superficial fibular);
• the dorsal foot muscles (EDB and EHB);
• the skin of the anterolateral leg and the dorsum of the foot.- Nerve roots
L4, L5, S1, S2 (posterior divisions).
- Course
Apex of the popliteal fossa → along the medial border of biceps femoris and its tendon → superficial to the lateral head of gastrocnemius → posterior to the fibular head → winds around the fibular neck (subcutaneous) → enters fibularis longus → superficial and deep fibular nerves.
- Branches
- Lateral sural cutaneous nerve.
• Sural communicating branch.
• Articular branches to the knee (including the recurrent articular nerve).
• Terminal branches: the superficial fibular and deep fibular nerves.
• In the thigh, its division of the sciatic nerve supplies the short head of biceps femoris.
Function
- Dorsiflexion of the ankle and extension of the toes (via the deep fibular nerve), which clears the foot during swing phase
- Eversion of the foot (via the superficial fibular nerve)
- Sensation of the lateral leg and the dorsum of the foot
Clinical significance
Foot drop at the fibular neck
Causes include fracture of the fibular neck, a tight plaster cast or brace, habitual leg crossing, prolonged squatting or kneeling, the lithotomy position, rapid weight loss and knee dislocation. The findings are:
• foot drop: inability to dorsiflex, so the foot slaps and the toes drag;
• a compensatory high-stepping (steppage) gait;
• the foot held plantarflexed and inverted (equinovarus) because of weak eversion;
• sensory loss over the anterolateral leg and dorsum of the foot.
The ankle reflex is preserved.
Fibular nerve palsy vs L5 radiculopathy
Both cause foot drop. An L5 root lesion, typically from an L4/5 disc, also weakens inversion (tibialis posterior, tibial nerve) and hip abduction (gluteus medius), and often causes back pain. In a common fibular nerve palsy, inversion and hip abduction are normal. Nerve conduction studies show slowing or block across the fibular head.
Compiled from standard anatomy and physiology references — see the Nervous System sources. For education only; not medical advice.