Common Peroneal Nerve
The common fibular (peroneal) nerve is a branch of the sciatic nerve. It supplies the anterior and lateral compartments of the legs, which enable dorsiflexion and ankle eversion respectively. The nerve also has sensory function on the dorsum of the foot and lateral surface of the leg. In this article we will discuss the anatomy of the nerve, as well as its clinical relevance. We will conclude with some review questions to test the reader’s understanding of the article content.
The sciatic nerve (ventral rami of L4-S3) descends along the posterior thigh and divides above the popliteal fossa into the common peroneal (ventral rami L4-S2) and tibial nerves (ventral rami of L4-S3). The tibial nerve continues to descend along the posterior thigh and leg, giving off articular branches to the knee joint, muscular branches to the posterior compartment of the leg and finally divides into the medial and lateral plantar nerves to provide sensorimotor innervation to the foot. The common fibular nerve passes laterally and gives off a small sural communicating branch that combines with a reciprocal communicating branch from the tibial nerve. The nerve that results from this combination is the Sural nerve, which relays sensation from the posterior and lateral surfaces of the distal third of the leg. The common fibular nerve innervates the short head of biceps femoris and passes lateral to its tendon at the level of the knee. It winds around the neck of the fibula to pass in the fibular tunnel between the fibula and the tendon of fibularis longus). It is vulnerable to crush injuries at this location, as it lies just beneath the skin.
The nerve then divides into a small articular branch supplying the knee joint, a superficial and a deep branch. The deep fibular nerve supplies the anterior compartment of the leg, i.e. tibialis anterior (evertor and dorsiflexor of the ankle), extensor hallucis longus (extensor of the big toe and dorsiflexor of the ankle), extensor digitorum longus (extensor of the 2nd to 5th toes and dorsiflexor of the ankle) and fibularis tertius (dorsiflexion and eversion of the foot). The deep division also relays sensation from the first web-space of the foot.
The superficial fibular nerve supplies motor innervation to the lateral compartment of the leg, i.e. fibularis longus and brevis (evertors of the ankle), which originate from the fibula. It also relays sensation from the lateral compartment of the leg (above the sural nerve) and dorsum of the foot (excluding the first dorsal web-space, and fifth toe).