Nerves - Common Fibular

Question 1

Nerve roots of the common fibular?

Answer 1

L4, L3, L2

Question 2

Motor function?

Answer 2

Innervates the short head of the biceps femoris directly. Also supplies muscles in the anterior and lateral compartments.

Question 3

Sensory function?

Answer 3

Innervates the skin of the lateral leg and dorsum of the foot.

Question 4

Anatomical course?

Answer 4

Begins at the apex of the popliteal fossa, where the sciatic nerve bifurcates and becomes the common fibular and tibial nerves.

Common fibular nerve follows the medial border of the biceps femoris, running in a lateral and inferior direction, over the lateral head of the gastrocnemius. It gives rise to two cutaneous branches, contributing to the skin of the leg.

To enter the lateral compartment, it wraps around the neck of the fibula, passing between attachments of the fibularis longus muscle. Here the common fibula terminates as the deep and superficial fibular nerves.

Question 5

Clinical relevance: damage to the common fibula

Answer 5

Aetiology - fracture of the fibula, or the use of a tight plaster cast.

These patients lose the ability to dorsiflex the foot at the ankle joint. Hence the foot will remain permanently plantar flexed - known as ‘foot drop’. They may also present with a characteristic gait.

Loss of sensation of the dorsum of the foot and lateral side of the leg. Innervation is preserved on the medial leg (supplied by the saphenous nerve, a branch of the femoral nerve), and heel and sole (supplied by the tibial nerve, a branch of the sciatic).