What’s the difference between myositis ossificans and heterotopic ossification?

Some doctors view these two conditions as two points on the same line. They are similar problems that cause pain, local signs of inflammation, and loss of motion.

In both cases, bone forms in and around soft tissue (usually muscle). Myositis ossificans (MO) occurs after trauma to the muscle or a broken bone. New bone cells form between the torn muscle fibers. This happens most often around the elbow or thigh. Children and young adults are affected most often.

Heterotopic ossification (HO) is more likely to occur after joint replacement surgery. Men over the age of 65 are affected most often. There are some known risk factors for HO. These include patients with ankylosing spondylitis or Paget’s disease. Hip joint replacement without cement is a risk factor. Both MO and HO occur after a stiff joint is manipulated under anesthesia.