Myositis ossificans (MO) is characterized by abnormal heterotopic bone formation involving striated muscle, tendons, ligaments, fasciae, and aponeuroses. Myocardium, the diaphragm, tongue, larynx, smooth muscle, and sphincters are all spared. Several subtypes of myositis ossificans exist: posttraumatic myositis ossificans (PTMO), nontraumatic/pseudomalignant myositis ossificans, and myositis ossificans progressiva (MOP). This article reviews the clinical features and differential diagnoses of each subtype of MO and illustrates the typical imaging features demonstrated by plain radiography, ultrasound, radionuclide bone scans, computed tomography, and magnetic resonance imaging.