Will exercise help prevent or promote myositis ossificans after a thigh hematoma?

It depends... Initially, rest, ice, immobilization and anti-inflammatory medications are indicated to minimize the extent of bleeding and damage in the muscle. After the initial inflammatory phase resolves, early passive and active range of motion exercises may help minimize the stiffness associated with myositis ossificans. Formal medical evaluation and a guided physical therapy program will optimize recovery.
It depends. After a thigh hematoma, you should receive physical therapy to restore range of motion , strength and function. Then it could be determined if you could return to exercise. If you exercise too soon, the hematoma could turn to an ossificans.