Myositis ossificans traumatica is a pathological condition characterized by extraskeletal bone formation, induced by major or repeated minor trauma to the muscles. Our objective is to report an unusual case of myositis ossificans traumatica in a paraplegic patient. Bilateral swelling and erythema on the thighs of a 1-month paraplegic inpatient was diagnosed as myositis ossificans traumatica in the quadriceps muscles due to low-molecular-weight heparin injections for deep vein thrombosis prophylaxis. As a result, repeated injections under the spinal cord injury level should be avoided when possible because of the risk of myositis ossificans traumatica.