The differential diagnosis of exercise-induced lower leg pain in young individuals is extensive and includes entities such as chronic exertional compartment syndrome, popliteal arterial entrapment syndrome, cystic adventitial disease, medial tibial stress syndrome and tibial stress fractures. Peripheral nerve-related lower leg pain syndromes are unusual. We present a 41-year-old woman who was diagnosed with an ancient schwannoma of the right common peroneal nerve (CPN) as a rare cause of lower leg pain. This case report provides simple diagnostic bedside tools that may be used to diagnose CPN abnormalities. Altered lateral lower leg skin sensation was found using a simple cotton swab, whereas a nodule was palpated at the fibular head. A positive Tinel sign indicated CPN dysfunction. MRI confirmed the diagnosis. Surgical resection is simple and curative.