Nerve · Knee

Common peroneal nerve

Nervus fibularis communis

The common peroneal nerve is the smaller division of the sciatic and the most commonly injured nerve in the lower limb — for a purely anatomical reason. After splitting off behind the knee it winds around the neck of the fibula, the bony bump on the outside just below the knee, where it lies directly against bone with only skin over it. Anything that presses there for long enough — sitting cross-legged, a tight plaster cast, a long squat, prolonged bed rest — can shut it down. Because it goes on to supply every muscle that lifts the foot and toes, the result is foot drop: the front of the foot will not lift, the toes catch on the floor, and the patient compensates with a high-stepping gait, with numbness over the top of the foot and the outer shin.