Kickboxing power hour: case report of fifth metatarsal apophysitis (Iselin disease) and its magnetic resonance imaging features

Youth now-a-days are getting more involved in mixed martial arts, with increasing number of cases of lateral foot pain due to various causes. The differential diagnoses of lateral foot pain in the pediatric population include avulsion fracture of the fifth metatarsal base, Jones fracture, diaphyseal stress fracture as well as os vesalianum pedis. We present a case of a 15-year-old athletic boy who presented with left lateral foot pain for a few weeks. The patient was actively involved in Kickboxing as well as active running. Left foot radiographs were normal, including normal radiographic appearance of the fifth metatarsal apophysis. Due to ongoing pain, magnetic resonance imaging of the left foot was performed, which revealed apophysitis of the fifth metatarsal, known as Iselin disease. Iselin disease has been postulated to be caused by traction on the fifth metatarsal apophysis by performing sidekicks or round kicks during the kickboxing practice. Iselin disease should be suspected in young children of 10–15 years age involved in physical activity presenting with lateral foot pain. Magnetic resonance imaging is extremely useful to correctly diagnose this condition and avoid misdiagnosis of a fracture.