In brief Myositis ossificans can be a troublesome complication of a muscle contusion, with significant downtime for an athletic patient, but the long-term prognosis is excellent Early diagnosis is important not only for administering expedient treatment, but also for advising the patient against activities that could compound the injury Typical findings include local swelling, tenderness, erythema, and regional warmth. X-rays will usually be negative until 2 to 4 weeks postinjury. Differentiation from osteogenic sarcoma can usually be made by history; location, and radiographic appearance. Early treatment includes rest, ice, compression, and anti-inflammatory drugs; once inflammation subsides, stretching and strengthening can begin.