The common peroneal (fibular) nerve winds around the neck of the fibula and is vulnerable to injury. Isolated common peroneal nerve palsy at the fibular neck produces which complete motor deficit?

• A Foot drop with loss of plantar flexion and inversion
• B Loss of toe flexion with intact ankle movements
• C Foot drop (inability to dorsiflex and evert the foot) with intact plantar flexion and inversion ✓
• D Loss of hip abduction with normal distal leg movement

Explanation

The common peroneal nerve divides into the superficial peroneal nerve (eversion via peroneus longus/brevis — anterior compartment variant) and the deep peroneal nerve (dorsiflexion via tibialis anterior, extensor digitorum longus/brevis, extensor hallucis longus). A lesion at the fibular neck paralyzes both divisions: loss of dorsiflexion AND eversion produces foot drop with the foot falling into plantar flexion and inversion. Plantar flexion (gastrocnemius, soleus) and inversion (tibialis posterior) are innervated by the tibial nerve (which is NOT affected), so these are intact. Hip abduction is innervated by the superior gluteal nerve.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.