Anatomy Msk · Year 1 · from Anatomy Msk
Case 1: Common Peroneal Nerve Palsy (Foot Drop)
Clinical Image
Source: Wikimedia Commons - Foot Drop - CC BY-SA 3.0
Case Presentation
A 58-year-old man presents with left foot weakness that he noticed upon waking two days ago. He had been hospitalized for pneumonia the prior week and recalls lying on his left side with his leg against the bedrail for prolonged periods. He reports difficulty lifting his foot when walking and has been tripping over his toes. Physical examination reveals weakness of left ankle dorsiflexion (tibialis anterior, 2/5), toe extension (EHL, EDL, 3/5), and foot eversion (peroneus longus and brevis, 3/5). Ankle plantarflexion (gastrocnemius, soleus) and foot inversion (tibialis posterior) are full strength. There is decreased sensation over the dorsum of the foot and lateral leg. Tinel sign is positive with tapping over the fibular neck. Knee and ankle reflexes are intact. He walks with a steppage gait, lifting his knee high to clear his foot. The clinical presentation is consistent with common peroneal nerve palsy from compression at the fibular neck. EMG/NCS at 3 weeks confirms neurapraxia of the common peroneal nerve. He is fitted with an ankle-foot orthosis (AFO) to prevent tripping and referred for physical therapy. At 3-month follow-up, he has recovered to 4/5 strength with continued improvement expected.
Key Learning Points
- The common peroneal nerve winds around the fibular neck superficially, making it vulnerable to compression
- The nerve divides into deep peroneal (anterior compartment) and superficial peroneal (lateral compartment) branches
- Peroneal nerve palsy causes foot drop (weakness of dorsiflexion), weak eversion, and dorsal foot sensory loss
- Steppage gait compensates for foot drop by lifting the knee higher to clear the toes
- Common causes: external compression (leg crossing, bed rest, casts), fibular fracture, knee dislocation