Dynamic sonography of external snapping hip syndrome.

Objective: To evaluate the dynamic sonographic findings of external snapping hip syndrome.

Methods: Five patients with 7 cases of painful external snapping hip (3 male and 2 female; age range, 14-32 years; mean, 19 years) were examined with sonography. Two patients had bilateral snapping. Dynamic sonographic examinations of hips were performed with a linear 5- to 12-MHz transducer during hip motion.

Results: Dynamic sonographic studies of the affected hip revealed causes of the external snapping hip in all cases. It was elicited by an abnormal jerky movement of the iliotibial band overlying the greater trochanter in 5 of 7 cases and of the gluteus maximus muscle in 2 cases. The iliotibial band over the greater trochanter was hypoechoic in 3 of the 5 cases and thickened in 1 case. Dynamic sonography showed good correlations between the jerky movements of the iliotibial band and the gluteus maximus muscle and the painful snapping reported by the patients.

Conclusions: Dynamic sonography was helpful in the diagnosis of external snapping hip syndrome; it showed real-time images of sudden abnormal displacement of the iliotibial band or the gluteus maximus muscle overlying the greater trochanter as a painful snap during hip motion.