Intra-articular Entrapment of the Common Peroneal Nerve in a Multiligamentous Knee Injury

Case: A 25-year-old severely obese woman sustained a knee injury with foot drop after an electric scooter crash. Initially diagnosed with a knee sprain and advised to follow-up with her primary care physician, she was later diagnosed with chronic multiligamentous knee instability and complete common peroneal nerve (CPN) palsy. Surgery 7 months postinjury demonstrated a severed intra-articular CPN scarred to the anterior cruciate ligament stump, necessitating arthroscopic-assisted extrication. Conclusion: Clinicians should maintain high suspicion for ligament injury and peroneal palsy after low-energy knee trauma in severely obese patients. Attentive neurovascular examination, imaging, and dissection are critical given possible aberrant nerve displacement.