title: Clinical decision rules discriminate between fractures and nonfractures in acute isolated knee trauma.
abstract: OBJECTIVE
  To develop criteria that optimize clinical decisionmaking in the use of radiography after isolated knee trauma in adults.
  
  
  METHODS
  A prospective survey of emergency department patients over a 7-month period. Standardized data forms were completed by emergency physicians, residents, and certified physician assistants.
  
  
  METHODS
  A large suburban community teaching hospital.
  
  
  METHODS
  Two hundred forty-two patients older than 17 years with isolated knee injuries sustained less than 24 hours previously.
  
  
  RESULTS
  We constructed a clinical decision model, calculating sensitivity, specificity, and odds ratios. Twenty-eight patients (11.6%) had fractures, with the patella the most commonly fractured osseous structure. Patients able to walk without limping had not experienced a fracture, nor had patients with twist injuries without effusion. Sensitivity of this model for detecting fracture was 1.0 (99% confidence interval, .97 to 1.0), and specificity was .337 (99% confidence interval, .26 to .42).
  
  
  CONCLUSIONS
  Clinical decision rules are effective in detecting knee fractures with 100% sensitivity and with sufficient specificity to eliminate 29% of knee radiographs in the ED. These findings require prospective validation.
authors.affiliation: Department of Emergency Medicine, William Beaumont Hospital, Royal Oak, Michigan, USA.
authors.forename: J E
authors.initials: JE
authors.lastname: Weber
authors.forename: R E
authors.initials: RE
authors.lastname: Jackson
authors.forename: W F
authors.initials: WF
authors.lastname: Peacock
authors.forename: R A
authors.initials: RA
authors.lastname: Swor
authors.forename: R
authors.initials: R
authors.lastname: Carley
authors.forename: G L
authors.initials: GL
authors.lastname: Larkin
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D003661:Decision Support Techniques; D003937:Diagnosis, Differential; D004630:Emergencies; D005260:Female; D050723:Fractures, Bone / Q000000981:diagnostic imaging*; D006801:Humans; D007718:Knee Injuries / Q000000981:diagnostic imaging*; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D011859:Radiography; D012680:Sensitivity and Specificity