Foot drop due to common peroneal nerve injury primarily involves which muscles?

Foot drop due to common peroneal nerve injury primarily involves which muscles?

• A. Gastrocnemius and Soles
• B. Flexor hallucis longus and Flexor digitorum longus
• C. Peroneus brevis and Peroneus longus
• D. Tibialis anterior and Extensor digitorum longus

Answer: (D)

Foot drop happens when the muscles that lift the front of the foot can’t function—mostly the dorsiflexors. The key players here are the tibialis anterior, which primarily drives dorsiflexion, and the extensor digitorum longus, which also assists on dorsiflexion and toe extension. Both are innervated by the deep branch of the common peroneal nerve, so injury to this nerve disrupts these muscles and the ability to pull the foot upward. The other muscle groups listed aren’t the main dorsiflexors. Gastrocnemius and soleus are plantarflexors (point the foot downward) and are innervated by the tibial nerve. The flexor muscles in the back of the leg also plantarflex and are supplied by the tibial nerve. The peroneus longus and brevis are everters (eversion of the foot) and are supplied by the superficial peroneal nerve. Losing those muscles doesn’t produce the classic inability to dorsiflex the foot seen in foot drop.

Foot drop happens when the muscles that lift the front of the foot can’t function—mostly the dorsiflexors. The key players here are the tibialis anterior, which primarily drives dorsiflexion, and the extensor digitorum longus, which also assists on dorsiflexion and toe extension. Both are innervated by the deep branch of the common peroneal nerve, so injury to this nerve disrupts these muscles and the ability to pull the foot upward.

The other muscle groups listed aren’t the main dorsiflexors. Gastrocnemius and soleus are plantarflexors (point the foot downward) and are innervated by the tibial nerve. The flexor muscles in the back of the leg also plantarflex and are supplied by the tibial nerve. The peroneus longus and brevis are everters (eversion of the foot) and are supplied by the superficial peroneal nerve. Losing those muscles doesn’t produce the classic inability to dorsiflex the foot seen in foot drop.