Common Fibular (Peroneal) Nerve
The Common Fibular
(L4-S2) typically separates from the sciatic nerve at the superior apex of the
popliteal fossa, the nerve follows the medial surface of biceps femoris (long
head initially) inferolaterally toward the knee. Superior to the knee the mass
formed by the lateral head of the gastrocnemius acts to "push" the
nerve onto the posterior edge of the biceps femoris tendon, which it follows
down to the fibular head. At this point, the common fibular nerve wraps around
the neck of the fibula, pierces the proximal anterolateral muscles and terminates
by dividing into superficial and deep fibular branches.
The common fibular nerve is the most frequently injured nerve of the lower limb, linked to its close relation to the head and neck of the fibula. Fractures of the fibular neck may traumatize the nerve directly, or peculiar leg-crossing postures compress the nerve. Prolonged maintenance of the squatting position (picking fruits or vegetables close to the ground) can lead to compression of the nerve against the fibula by the tight tendon of the biceps femoris. All these yield motor symptoms of anterior tibial compartment paralysis and weakness of the fibularis longus and brevis. When there is paralysis of the anterior compartment muscles, the ankle cannot be actively dorsiflexed, but the requirement for the forefoot to clear the group during swing phase is accommodated by excessive flexion at the hip and knee. The "foot drop" produces the so-called "high-stepping" gait. Since the foot cannot be actively dorsiflexed, normal landing on the heel is impossible.