Ultrasonographic Study of the Quadriceps Muscle Rotation for Pathogenesis of Recurrent Patellar Dislocation : Comparison by Sex and Age

Recurrent patellar dislocation occurs mainly in young women, pathogenesis of which being considered to involve the abnormal knee extenser mechanism. Then, using ultrasonography, comparative study was made of the rotatory condition of the quadriceps muscle between healthy subjects in growing period and dislocated patients to consider its pathogenesis. The subjects were 129 normal males and 124 normal females from 3 to 18 years of age, and 18 females with the dislocation. Using ultrasonography, the direction of lateral intermuscular septum of the quadriceps muscle and posterior condyles of the femur were detected. From the picture of scanning, the angle （E. R. A. ） between the saggital plane and the direction of lateral intermuscular septum of the quadriceps muscle was calculated and corrected by the angle between the horizontal plane and the tangent of the posterior condyles of the femur as an index of external rotation of the quadriceps muscle. Comparison of E. R. A. by sex and by age in healthy subjects and that between healthy subjects and dislocated patients were made. As a result, for healthy normal subjects, mean E. R, A. was significantly greater in females, but no significant inter－age difference was noted in either sex. E. R. A. on the affected side for female dislocated patients was significantly greater compared with healthy females. These results suggested that E. R. A. was greater by nature in females than in males and was far greater especially for dislocated patients, which was partially responsible for the occurrence of the recurrent patellar dislocatio