Pictorial essay. Myositis ossificans circumscripta.

Myositis ossificans circumscripta (MOC) is a localized, non-neoplastic, heterotopic ossification within the muscle. Despite advances in medical imaging, it remains difficult to distinguish it from other disorders. As a consequence, a biopsy is frequently performed. We illustrate some common findings and non-specific imaging features of MOC with respect to radiography, computed tomography, bone scintigraphy, ultrasonography, and magnetic resonance imaging. The differentiation among MOC and its mimics is also presented in order to help the radiologists to make an appropriate diagnostic decision.