Myositis Ossificans Traumatica, ossifying hematoma and calcifying hematoma have been used interchangeably to dcscribe the process of calcification and ossification occuring within muscle tissue in response to trauma. Authors analysed 27 cases of traumatic myositis ossificans of the Quadriceps who were diagnosed and treated at the department of orthopaedic surgery, National Police Hospital from January 1978 to June 1984. The results are as follows: 1. In sex distribution, in all cases 27 were males, in age distribution they were between 19 and 25 years old. 2. The causes of trauma consisted of 11 in kicking and treading, 6 in falling and slipping, 6 in football, 4 in demonstration injury. 3. The duration from injury to initial visit was variable. The average duration was 2 weeks. 4. Quadriceps contusions in all cases were grouped according to severity of trauma as mild, moderate and severe. Among 27 cases, 4 cases were mild, 11 cases were moderate, 12 cases were grouped as severe. According to the severity of trauma, duration of treatment and restoration of affected knee joint motion were more prolonged. 5. Among 27 cases, 6 cases sustained reinjury. 6. Total 27 cases, average duration of treatment was 4.6 weeks. 7. In those patients presenting after 2 weeks from injury, the duration of treatment was 3.8 weeks, and in those patients presenting within 2 weeks it was 5.4 weeks. Thc moderate cases were required 3.8 weeks of the duration of treatment, severe cases were required 6.5 weeks. Reinjury cases, 6 cases required more prolonged treatment, 6.8 weeks. These results suggest that early treatment, low violence of trauma and prevention of reinjury were the factor of minimizing the impairment of knee joint motion and shortening the duration of treatment. 8. The earlist X-ray change was found of the 14th day from injury. (average the 27th day from injury). 9. Within 6 months, all cases regained full range of motion of knee joint. 10. With only conservative treatment applied on all cases, we get the satisfactory result.