Non-traumatic myositis ossificans circumscripta in the context of vastus medialis obliquus: A case report

Myositis ossificans circumscripta (MOC) is an heterotopic proliferation of non-tumoral cells of the bone and cartilage tissues. Traumas play an important role in the development of MOC. When the patient reports no trauma, the clinicians should suspect an underlying systemic pathology, such as hemophilia, causing unrecognized hemorrhages, or other conditions as muscular disorders, infections, tetanus and drug abuse. Clinically and radiologically it is difficult to distinguish this benign disease from soft tissues (such as osteomyelitis) and bone malignancy (such as sarcoma). In the current literature there are only few case reports about the occurring of myositis ossificans circumscripta without traumas, and there are no case series. We report a rare non-traumatic case of MOC in an active 40-year-old woman, in the context of the middle-inferior third of vastus medialis obliquus in the right thigh, treated with excisional biopsy and indomethacin prophylaxis. After six months of follow-up, the patient had complete clinical and radiological recovery.