Common Peroneal (Fibular) Nerve Injury
The common peroneal nerve is the most frequently injured in the lower extremity, primarily due to its superficial course around the fibular neck.
Etiology
- Trauma: Fracture of the proximal fibula or direct blow to the lateral knee.
- Compression: Prolonged immobilization (casts), habitual leg crossing, or tight boots/compressive dressings.
Clinical Presentation
| Feature | Finding |
|---|---|
| Motor | Foot drop (loss of dorsiflexion); loss of eversion (superficial peroneal nerve). |
| Sensory | Loss of sensation over the anterolateral lower leg and the dorsum of the foot. |
| Gait | Steppage gait (patient lifts the knee high to clear the toes during the swing phase). |
High-Yield Exam Pearl:
Always differentiate a common peroneal nerve injury from an L5 radiculopathy. Both cause foot drop; however, L5 radiculopathy also involves weakness in hip abduction (gluteus medius) and inversion (tibialis posterior), whereas isolated common peroneal injury preserves these functions.