Non-tumoral heterotopic bone proliferation within soft tissues, and more specifically in striated skeletal muscles, is known as myositis ossificans.
The most frequently encountered form is the acquired form which is benign and often trauma-related, but can also appear without any trigger. It develops through three stages (acute, subacute, and mature). Diagnosis can be difficult, especially during the acute phase where the clinical presentation can mimic other pathologies, such as muscle abscess or sarcoma. It is important to identify the disease at this stage, as it avoids unnecessary recourse to biopsy. When mature, myositis ossificans has a well-defined appearance, hence the name myositis ossificans circumscripta. In all cases, the diagnosis will require imaging exams. The pathophysiological mechanism of myositis ossificans has not yet been fully elucidated, but there are several theories.
This article illustrates the diagnosis and management of acquired and circumscribed myositis ossificans on the basis of a clinical case.