M. Peroneus Quartus Causing Chronic Peroneal Compartment Syndrome in a Runner Treated by Endoscopic Fasciotomy: A Case Report.

We present the rare case of a 47-year-old male long-distance runner who was referred to our hospital with a longstanding pain in his left calf. Clinical history, as well as ultrasound and magnetic resonance imaging scans, showed an accessory peroneal muscle. This muscle was identified as a peroneus quartus muscle. On ultrasound, controlled intracompartmental pressure measurement, a chronic peroneal compartment syndrome, was diagnosed. We performed an endoscopic-assisted fasciotomy of the peroneal compartment. This resolved the patient's symptoms completely and allowed the runner to return to competition shortly after the surgery.