Myositis ossificans in early childhood.

A 5-year-old boy underwent arthroscopic surgery because of a lateral discoid meniscus, which was followed by an overly strenuous rehabilitation program. At 6-week follow-up, a painful mass at the distal part of the thigh and a flexion restriction of the operated knee were detected, caused by myositis ossificans inside the vastus medialis muscle. The symptoms disappeared with an appropriate rehabilitation program and the patient recovered.