In 2020, the World Health Organization classified myositis ossificans together with fibro-osseous pseudotumor of digits as a single specific entity in the category of fibroblastic and myofibroblastic tumors.

This is followed by intermediate phase of bone formation (four to eight weeks following injury) where calcification started to occur and is visible on X-rays.

In the late stage, termed mature, myositis ossificans is depicted as an elongated calcific deposit that is aligned with the long-axis of the muscle, exhibits acoustic shadowing, and has no soft tissue mass associated.

A main concern is to differentiate early myositis ossificans from malignant soft-tissue tumors, and the latter is suggested by a fast-growing process.

At histology, detection of the typical zonal phenomenon is diagnostic of myositis ossificans, though microscopic findings may be misleading during the early stage.

As the calcifications will typically resolve after a period of time, non-surgical treatment is encouraged to minimize the unpleasant symptoms and maximize the function of the affected limb.

If the lesion becomes more mature, active range of motion and resistance strengthening exercises are useful in maintaining joint function.

[5] Surgical excision is reserved for those who failed the non-surgical treatment, those with intolerable pain, compression of the neurovascular structures, or limitation of the range of motion of the joint which affects the activities of daily living.