title: Dynamic sonography of external snapping hip syndrome.
abstract: 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.
authors.affiliation: Department of Diagnostic Radiology, Eulji Hospital, Eulji University School of Medicine, Seoul, South Korea.
authors.forename: Yun Sun
authors.initials: YS
authors.lastname: Choi
authors.forename: Sung Moon
authors.initials: SM
authors.lastname: Lee
authors.forename: Baek Yong
authors.initials: BY
authors.lastname: Song
authors.forename: Sang Hyun
authors.initials: SH
authors.lastname: Paik
authors.forename: Yong Kyu
authors.initials: YK
authors.lastname: Yoon
mesh_terms: D000328:Adult; D005260:Female; D006621:Hip Joint / Q000000981:diagnostic imaging* / Q000503:physiopathology; D006801:Humans; D007592:Joint Diseases / Q000000981:diagnostic imaging* / Q000503:physiopathology; D008297:Male; D018482:Muscle, Skeletal / Q000000981:diagnostic imaging / Q000503:physiopathology; D013577:Syndrome; D014159:Transducers; D014463:Ultrasonography