Injuries to the lateral portion of the knee and fibula often commonly injure the common fibular/common peroneal nerve. Functions of the common fibular nerve include: sensation of the dorsum of the foot, dorsiflexion and eversion of the foot.

Other answer choices

B) Femoral nerve supplies none of the muscles below the knee, although the saphenous nerve, one of its branches, travels medial to the tibia (like the great saphenous vein). The femoral nerve supplies the quads, sartorius, iliacus, and pectineus muscles.

C) Obturator nerve, again, supplies none of the muscles below the knee. It innervates the obturator externus, pectineus (dual innervation), the three adductor muscles, and the gracilis muscle. Contrary to intuition, the obturator nerve does not innervate the obturator internus muscle, which is innervated by "nerve to obturator internus."

D) The sural nerve supplies only cutaneous innervation. It is a branch of both the common fibular and the tibial nerves, so maybe it will be injured in this case, but it won't cause muscular deficits.

E) The tibial nerve is the most tempting alternative option. It supplies the muscles of the calf, which effect plantar flexion and ankle inversion.