Common Peroneal Nerve is a small terminal branch of the Sciatic nerve. Its point of appearance is just above popliteal fossa in the lower third of thigh. The entrance point in popliteal fossa is just below biceps tendon’s border along with upper lateral boundary of popliteal fossa . Then it goes over lateral head of gastrocnemius and plantaris. Afterwards it divides into two farthest branches the deep and superficial peroneal nerves when it twists around the lateral part of neck of fibula to reach deeper to peroneous longus while going over fibular connection of the soleus.
The motor branches of the deep peroneal nerve supply all the muscles of the anterior compartment of the leg consisting of extensor digitorum brevis on the dorsum of the foot.
The motor branches of the superficial peroneal nerve supply all the muscles of the lateral compartment of the leg.
The sensory branches of the deep peroneal nerve supply the skin of cleft between the great and second toes.
The sensory branches of the superficial peroneal nerve supply majority of the skin on the dorsum of foot with the exception of in the cleft between the great and second toes being supplied by the deep peroneal nerve. The lateral margin of the dorsum of foot consisting of the lateral margin of little toe is supplied by the sural nerve. The medial margin of the dorsum of foot up to the ball of the great toe is being supplied by the saphenous nerve.
In the popliteal fossa, the common peroneal nerve Supplies rise to two cutaneous branches and three genicular branches.
All these are as follows:
- Sural conveying nerve: It originates opposite to the head of the fibula, and crosses superficially to the lateral head of gastrocnemius to join the sural nerve.
- Lateral cutaneous nerve (lateral sural nerve): It originates lower down and pierces the deep fascia to supply the skin on the upper part of the lateral side of the leg.
Genicular (articular) branches
All these are superior lateral genicular, inferior lateral genicular, and recurrent genicular nerves. The former two supply the knee joint and the latter one supplies the superior tibiofibular joint.
The common peroneal nerve can be palpated against the neck of fibula. And the common peroneal nerve supplies no muscular branch in the popliteal fossa.
Effects of Injury To The Common Peroneal Nerve
The common peroneal nerve is very susceptible to injury as it winds around the posterolateral aspect of the neck of the fibula. At this site, it might be injured by the direct trauma, fracture neck of fibula, or closely applied plaster cast. The characteristic clinical features are as follows:
- Foot drop, as a result of paralysis of muscles of the anterior compartment of the leg (dorsiflexors of the foot).
- Loss of extension of toes, because of the paralysis of extensor digitorum longus and extensor hallucis longus.
- Loss of eversion of foot, because of the paralysis of peroneus longus and peroneus brevis (evertors of the foot).
- The sensory loss because of participation of the cutaneous branches, on the anterolateral aspect of the leg, and entire of dorsum foot with the exception of the regions supplied by the saphenous and sural nerves.
Because of paralysis of the dorsiflexors and evertors of the foot, the patient can not stand on the heel. He’s high-stepping gait, where foot is lifted higher compared to the normal so that the toes don’t hit the earth. Moreover, if the foot is put back on the earth unexpectedly, it generates a smacking sound termed foot smack.