title: What is the impingement-free range of motion of the asymptomatic hip in young adult males?
abstract: BACKGROUND
  Femoroacetabular impingement is a recognized cause of chondrolabral injury. Although surgical treatment for impingement seeks to improve range of motion, there are very little normative data on dynamic impingement-free hip range of motion (ROM) in asymptomatic people. Hip ultrasound demonstrates labral anatomy and femoral morphology and, when used dynamically, can assist in measuring range of motion.
  
  
  OBJECTIVE
  The purposes of this study were (1) to measure impingement-free hip ROM until labral deflection is observed; and (2) to measure the maximum degree of sagittal plane hip flexion when further flexion is limited by structural femoroacetabular abutment.
  
  
  METHODS
  Forty asymptomatic adult male volunteers (80 hips) between the ages of 21 and 35 years underwent bilateral static and dynamic hip ultrasound examination. Femoral morphology was characterized and midsagittal flexion passive ROM was measured at two points: (1) at the initiation of labral deformation; and (2) at maximum flexion when the femur impinged on the acetabular rim. The mean age of the subjects was 28 ± 3 years and the mean body mass index was 25 ± 4 kg/m(2).
  
  
  RESULTS
  Mean impingement-free hip passive flexion measured from full extension to initial labral deflection was 68° ± 17° (95% confidence interval [CI], 65-72). Mean maximum midsagittal passive flexion, measured at the time of bony impingement, was 96° ± 6° (95% CI, 95-98).
  
  
  CONCLUSIONS
  Using dynamic ultrasound, we found that passive ROM in the asymptomatic hip was much less than the motion reported in previous studies. Measuring ROM using ultrasound is more accurate because it allows anatomic confirmation of terminal hip motion.
  
  
  CONCLUSIONS
  Surgical procedures used to treat femoroacetabular impingement are designed to restore or increase hip ROM and their results should be evaluated in light of precise normative data. This study suggests that normal passive impingement-free femoroacetabular flexion in the young adult male is approximately 95°.
authors.affiliation: Rose Medical Center, Denver, CO, USA.
authors.forename: Brian
authors.initials: B
authors.lastname: Larkin
authors.forename: Marnix
authors.initials: M
authors.lastname: van Holsbeeck
authors.forename: Denise
authors.initials: D
authors.lastname: Koueiter
authors.forename: Ira
authors.initials: I
authors.lastname: Zaltz
mesh_terms: D000328:Adult; D058070:Asymptomatic Diseases; D001696:Biomechanical Phenomena; D057925:Femoracetabular Impingement / Q000175:diagnosis / Q000503:physiopathology; D006621:Hip Joint / Q000000981:diagnostic imaging / Q000502:physiology*; D006801:Humans; D008297:Male; D016059:Range of Motion, Articular; D012016:Reference Values; D014463:Ultrasonography; D055815:Young Adult