A 35-year-old patient develops foot drop and sensory loss over the dorsum of the foot and lateral leg after prolonged squatting. The nerve injured most commonly at the fibular neck is the common fibular (peroneal) nerve. Which specific division causes foot drop (loss of dorsiflexion and eversion)?

• A Superficial fibular nerve alone is responsible for all dorsiflexion and eversion movements
• B Tibial nerve injury at the knee causes foot drop due to loss of gastrocnemius
• C Deep fibular nerve paralysis causes loss of dorsiflexion; superficial fibular nerve paralysis causes loss of eversion — both are needed for complete drop foot ✓
• D Deep fibular nerve alone causes both foot drop and eversion loss

Explanation

The common fibular nerve divides at the fibular neck into the deep fibular nerve (supplying dorsiflexors: tibialis anterior, extensor digitorum longus, extensor hallucis longus) and the superficial fibular nerve (supplying everters: fibularis longus and brevis). Foot drop (inability to dorsiflex) results from deep fibular nerve injury; loss of eversion from superficial fibular nerve injury. A complete common peroneal nerve injury causes both. The tibial nerve supplies plantar flexors (gastrocnemius, soleus) and foot invertors. Sensory loss on the dorsum of foot and lateral leg confirms superficial fibular territory involvement.

Reference: BD Chaurasia's Human Anatomy, 8th ed.

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Written and medically reviewed by the StethoPrep medical team.