Myositis ossificans

This is a case of a 42 year old woman who presents with hip pain following a car accident 1 month ago. Frontal radiograph of the femur demonstrates soft tissue calcification adjacent to the femoral diaphysis. On lateral radigraph, there is a serpiginous calcification within the soft tissues overlying the femur, likely within the quadriceps musculature. On close inspection, the periphery of the lesion is calcified while the central portion is lucent. This finding is referred to as the "zonal phenomenon" which is characteristic of an entity called myositis ossificans. Myositis ossificans refers to painful postraumatic calcification which typically occurs within muscles. It is a diagnosis that is critical to recognize as it can be easily mistaken by MRI for a primary sarcoma. Additionally, biopsy should be avoided when possible as the lesion contains multifocal sites of osteogenesis, which can easily be mistaken for osteosarcoma.