COMMON PERONEAL NERVE ANATOMY

Sciatic nerve originates form the L4 thru’ S2 roots. It leaves pelvis by passing thru’ the greater sciatic foramen and enters thigh. In the upper popliteal fossa, it divides into common peroneal and tibial nerves. Within the sciatic nerve, the fibers that eventually form the common peroneal and tibial division run separately from each other.

In the upper thigh, tibial division provides innervation to all hamstring muscles except short head of biceps femoris which is supplied by the peroneal division. Thus, short head of biceps femoris is the only peroneal innervated muscle above knee joint.

Soon after separating from tibial division, the common peroneal gives off the lateral cutaneous nerve of the calf, which innervates the skin over the upper third of the lateral aspect of the leg (not highlighted in figure). Then the peroneal nerve winds around the fibular neck and divides into its terminal braches, the superficial and deep peroneal nerves.







Superficial peroneal nerve
The superficial peroneal nerve is predominantly sensory; it innervates the skin of the lower two thirds of the lateral aspect of the leg and the dorsum of the foot and sends motor branches to the peroneus longus and brevis.














Deep peroneal nerve
The deep peroneal nerve is predominantly motor; it innervates tibialis anterior, extensor hallucis, extensor digitorum longus & brevis (all ankle and toe extensors) and peroneus tertius. It sensory branches supply the skin of the web space b/w the first and second toe.


Reference:

1. Richard S Snell, Clinical Anatomy: Lippincott Williams & Wilkins, 7th edition
   
2. Preston DC. Distal Median Neuropathies. In: Entrapment and other focal neuropathies; Neurologic Clinics: WB Saunders company, August 1999
   
3. Katriji MB, Wilbourn AJ. Common peroneal neuropathy: a clinical and electrophysiologic study of 116 lesions. Neurology 1988;38:1723.