Rare Insertional Peroneus Brevis Tendon Tear at the Base of the Fifth Metatarsal Despite a Reassuring MRI Report: A Case Report

Introduction Peroneus brevis tendon tears are a recognised cause of lateral foot and ankle pain and are most commonly described as longitudinal split tears within the retromalleolar groove. Isolated insertional tears at the base of the fifth metatarsal are rarely reported and may present a diagnostic challenge, particularly when imaging findings are subtle. Case Report We present a case of an atraumatic insertional longitudinal tear of the peroneus brevis tendon in a 60-year-old female with persistent lateral foot pain despite extensive conservative management. The formal magnetic resonance imaging (MRI) report described the peroneal tendons as normal; however, independent review by the treating foot and ankle surgeons identified subtle abnormalities at the tendon insertion that were considered inconsistent with a completely normal tendon appearance. Given the persistent symptoms, clinical findings, and surgeon-reviewed imaging abnormalities, surgical exploration was undertaken. Intraoperatively, multiple longitudinal split tears of the peroneus brevis tendon were identified at its insertion on the base of the fifth metatarsal and successfully repaired. At 12-month follow-up, the patient reported complete resolution of symptoms and return to normal activities. Discussion This case represents an uncommon presentation of peroneus brevis tendon pathology occurring at the tendon insertion rather than the more commonly described retromalleolar location. It also highlights the importance of clinical-radiological correlation and surgeon-led image review when evaluating persistent lateral foot pain. Conclusion Insertional peroneus brevis tendon tears should be considered in patients with persistent lateral foot pain despite apparently reassuring imaging findings. Careful review of imaging studies in conjunction with clinical assessment may help identify subtle pathology and guide appropriate surgical management.