title: Is a positive femoroacetabular impingement test a common finding in healthy young adults?
abstract: BACKGROUND
  Femoroacetabular impingement (FAI) is an incompletely understood clinical concept that implies pathomechanical changes in the hip as a cause for hip-related pain in young adults. While a positive anterior impingement test is suggestive of FAI, its association with clinical and radiographic findings remain unconfirmed in healthy young adults.
  
  
  OBJECTIVE
  We determined the prevalence of a positive test in 1170 young adults and examined its possible associations with (1) self-reported hip discomfort for the past 3 months; (2) weekly physical exercise; (3) hip ROM; and (4) radiographic findings associated with femoroacetabular impingement.
  
  
  METHODS
  We invited 2344 healthy 19-year-olds to a population-based hip study between 2008 and 2009; 1170 patients (50%) consented. The study included questionnaires on medical and functional status, a clinical hip examination including the impingement test and hip ROM, and two pelvic radiographs (AP and frog-leg views).
  
  
  RESULTS
  Based on at least one affected hip, 35 of 480 (7.3%) men and 32 of 672 (4.8%) women had positive impingement tests. Eighteen of the 1170 patients were excluded owing to suboptimal or missing radiographs. Self-reported hip discomfort in the women and increased physical exercise in the men were strongly associated with the positive impingement tests. Decreased abduction and internal rotation in the men, decreased flexion in both genders, and radiographic cam type findings in the men also were associated with positive tests.
  
  
  CONCLUSIONS
  A positive test for anterior impingement is not uncommon in healthy young adults, especially in males. We believe it always should be performed along with pelvic radiographs in young, active patients presenting with hip pain.
  
  
  METHODS
  Level II, diagnostic study. See the Guidelines for Authors for a complete description of level of evidence.
authors: Department of Surgical Sciences, University of Bergen, Bergen, Norway. lene.bjerke.laborie@helse-bergen.no
authors: Lene B
authors: LB
authors: Laborie
authors: Trude G
authors: TG
authors: Lehmann
authors: Ingvild Ø
authors: IØ
authors: Engesæter
authors: Lars B
authors: LB
authors: Engesæter
authors: Karen
authors: K
authors: Rosendahl
mesh_terms: D000293:Adolescent; D018771:Arthralgia / Q000175:diagnosis / Q000453:epidemiology; D001696:Biomechanical Phenomena; D005260:Female; D057925:Femoracetabular Impingement / Q000175:diagnosis* / Q000000981:diagnostic imaging / Q000453:epidemiology / Q000503:physiopathology; D006621:Hip Joint / Q000000981:diagnostic imaging* / Q000503:physiopathology*; D006801:Humans; D008297:Male; D009664:Norway / Q000453:epidemiology; D010808:Physical Examination; D011237:Predictive Value of Tests; D015995:Prevalence; D011859:Radiography; D016059:Range of Motion, Articular; D012720:Severity of Illness Index; D011795:Surveys and Questionnaires; D055815:Young Adult