Myositis ossificans is characterised by heterotopic ossification within large muscles. It can be inherited but typically occurs 2-6 weeks after trauma, with the most common sites being the elbow and the thigh. It can mimic osteal malignancy and can even histologically appear like osteosarcoma, leading to incorrect management.
It is benign and treated conservatively in most cases. Surgical excision may be attempted if very severe.