title: Validation of the Ottawa Knee Rules.
abstract: OBJECTIVE
  We sought to validate the Ottawa Knee Rules for determining the need for radiography in patients with acute knee injury.
  
  
  METHODS
  A prospective cohort study was performed in emergency departments of 11 hospitals of the Osakidetza-Basque Country Health Service. The patient population was composed of a convenience sample of 1,522 eligible adults of 2,315 patients with acute knee injuries. The attending emergency physicians assessed each patient for standardized clinical variables and determined the need for radiography according to the decision rule. Radiography was performed in each patient, irrespective of the determination of the rule, after clinical evaluation findings were recorded. The rule was assessed for the ability to correctly identify fracture of the knee.
  
  
  RESULTS
  The decision rule had a sensitivity of 1.0 (95% confidence interval [CI] 0.96 to 1.0), identifying 89 patients with clinically important fractures. The potential reduction in use of radiography was estimated to be 49%. The probability of fracture, if the decision rules were negative, is estimated to be 0% (95% CI 0% to 0.5%).
  
  
  CONCLUSIONS
  Prospective validation has shown the Ottawa Knee Rules to be 100% sensitive for identifying fractures of the knee and to have the potential to allow physicians to reduce the use of radiography in patients with acute knee injuries.
authors.affiliation: Clinical Epidemiology Unit, Hospital Aránzazu, CHDO, San Sebastian, Basque Country, Spain. jemparan@chdo.osakidetza.net
authors.forename: J I
authors.initials: JI
authors.lastname: Emparanza
authors.forename: J R
authors.initials: JR
authors.lastname: Aginaga
mesh_terms: D000208:Acute Disease; D000328:Adult; D015331:Cohort Studies; D016001:Confidence Intervals; D004636:Emergency Service, Hospital / Q000592:standards*; D004638:Emergency Treatment / Q000592:standards; D005260:Female; D017408:Guidelines as Topic; D006801:Humans; D015601:Injury Severity Score; D007718:Knee Injuries / Q000175:diagnosis / Q000000981:diagnostic imaging* / Q000628:therapy; D008297:Male; D020380:Needs Assessment; D011446:Prospective Studies; D011859:Radiography / Q000706:statistics & numerical data*; D012494:Sampling Studies; D012680:Sensitivity and Specificity; D013030:Spain