Myositis ossificans is a disease in which progressive bone structures are deposited in muscles and connective tissues, causing muscle sclerosis and deformities of toes and hallux. The cause is unclear. Some cases are inherited as autosomal dominant diseases. It is common in children or young people. It manifests as abnormal congenital torticollis, twisting, and swelling and hardening of the neck muscles, but most cases are not accompanied by pain. Muscles throughout the body can be affected. Vigorous exercise or trauma can cause muscle rupture, bleeding, and hematoma formation. In most patients, the hematoma is absorbed, but muscle stiffness and ossification may also occur, eventually causing stiffness and disability of the corresponding joints of the affected muscles.