COMMON PERIONEAL NERVE / FIBULAR NERVE

• The common peroneal nerve, about one-half the size of the tibial nerve, arises from the dorsal branches of the fourth and fifth lumbar and the first and second sacral nerves.

• It descends obliquely along the lateral side of the popliteal fossa to the head of the fibula, close to the medial margin of the biceps femoris muscle. 

• Where the common peroneal nerve winds round the head of the fibula, it is palpable.

• It lies between the tendon of the biceps femoris and lateral head of the gastrocnemius muscle, winds around the neck of the fibula, between the peroneus longus and the bone, and divides beneath the muscle into the superficial peroneal nerve and deep peroneal nerve.

BRANCHES:

1) Cutaneous branches 

i) Lateral cutaneous nerve of calf:

• Supply the skin of the upper two-thirds of the lateral side of the leg.

ii) Peroneal communicating nerve: Joins the sural nerve.   

2) Articular branches

• Superior lateral genicular

• Inferior lateral genicular

• Recurrent genicular

3) The motor branches:

• As the common peroneal nerve exits the popliteal fossa, it courses around the lateral aspect of the leg just below the head of the fibula. 

• Here it is apposed with fibula and gives off two branches, the superficial peroneal branch and deep peroneal branch.

i) The superficial peroneal nerve:

• Main nerve of lateral compartment of leg.

• supplies the muscles of the lateral compartment of the leg namely: peroneus longus and peroneus brevis.

• These two muscles assist with eversion and plantar flexion of the foot.

• Medial branch breaks to supply the medial side of big toe.

ii) The deep peroneal nerve:

• innervates the muscles of the anterior compartment of the leg which are: tibialis anterior, extensor hallucis longus, extensor digitorum longus, and the peroneus tertius.

• Together these muscles are responsible for dorsiflexion of the foot and extension of the toes.

• The deep peroneal nerve also innervates intrinsic muscles of the foot including the extensor digitorum brevis and the extensor hallucis brevis.

• The common peroneal nerve innervates the short head of the biceps femoris muscle via a motor branch that exits close to the gluteal cleft.

• The remainder of the peroneal-innervated muscles are innervated by its branches, the deep peroneal nerve and superficial peroneal nerve.

• It provides sensory innervation to the skin over the upper third of the lateral aspect of the leg via the lateral cutaneous nerve of the calf. It gives the peroneal communicating nerve which joins the sural nerve in the midcalf.