***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
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    Input: Background This study was design ed to determine the accuracy of the Ottawa Knee Rule ( OKR ) when applied to patients with acute knee injury in the Iranian population of the Imam Hospital Emergency Department ( ED ) at . Methods This prospect i ve cohort validation study included a convenience sample of all patients with a blunt knee injury sustained in the preceding 7 days presenting to the ED of a tertiary care teaching hospital during the study period . Patients were assessed for the five variables comprising the OKR , and a st and ardised data form was completed for each patient . St and ard knee radiographs were ordered on all patients irrespective of the determination of the rule . The rules were interpreted by the primary investigator on the basis of the data sheet and the final orthopaedist radiograph reading . Outcome measures of this study were : sensitivity , specificity , positive predictive value and negative predictive value of the OKR .  Results A total of 283 patients were enrolled in the study . 22 fractures ( 7.77 % ) were detected . The decision rule had a sensitivity of 0.95 ( 95 % CI 0.77 to 0.99 ) , and a specificity of 0.44 ( 95 % CI 0.37 to 0.50 ) . The potential reduction in use of radiography was estimated to be 41 % . The OKR missed only one fracture . Conclusion Prospect i ve validation has shown that the OKR is a highly sensitive tool for detecting knee fractures and has the potential to reduce the number of radiographs in patients with acute knee injuries OBJECTIVE To determine interobserver agreement between triage registered nurses ( RNs ) and emergency physicians ( EPs ) regarding indication for knee radiographs by applying the Ottawa knee rule ( OKR ) and individual components of the rule . METHODS This was a prospect i ve , observational study in a suburban , teaching emergency department . The study enrolled a convenience sample of patients aged > 17 years with traumatic knee injuries less than one week old . Patients with prior knee surgery or distracting conditions were excluded . Before study initiation , the RNs and EPs were in-serviced in the OKR . Nurses and EPs independently examined each patient for OKR criteria , blinded to the other 's assessment .  Knee radiographs were ordered at the discretion of the EP and were interpreted by board-certified radiologists . All patients received follow-up with a structured telephone interview to identify any undetected fractures . Kappa was calculated for each component and the overall application of the OKR to assess interobserver agreement . RESULTS Ninety-six patients were enrolled . The mean age was 39.6 + /- 18.7 years ; 50 % were male . Eight patients ( 8 % ) had knee fractures . Interobserver agreements between the RNs and EPs for individual components of the OKR were : age > or = 55 years ( kappa = 0.97 ) ; inability to weight bear ( kappa = 0.51 ) ; inability to bend knee to 90 degrees ( kappa = 0.52 ) ; fibular head tenderness ( kappa = 0.45 ) ; and isolated patellar tenderness ( kappa = 0.40 ) . The EPs and RNs agreed with OKR criteria for x-ray 71 % of the time ( kappa = 0.41 ) . CONCLUSIONS The only criterion that result ed in almost perfect agreement between the RNs and EPs was patient age ; agreement for the other four criteria and the overall decision to order x-rays was moderate OBJECTIVE To vali date a previously derived decision rule for the use of radiography in patients with acute knee injury . DESIGN Prospect ively administered survey . SETTING Emergency departments of two university hospitals serving adults . PATIENTS Convenience sample of 1096 of 1251 eligible adults with acute knee injuries ; 124 patients were examined by two physicians . MAIN OUTCOME MEASURES Attending emergency physicians assessed each patient for st and ardized clinical variables and determined the need for  radiography  according to the decision rule . Patients who did not have radiography  underwent a  structured telephone interview  at day 14 to determine the possibility of a fracture . The rule was assessed for ability to correctly identify the criterion st and ard , fracture of the knee . An attempt was made to refine the rule by means of univariate and recursive partitioning analyses . RESULTS The decision rule had a sensitivity of 1.0 ( 95 % confidence interval [ CI ] , 0.94 to 1.0 ) for identifying 63 clinical ly important fractures . Physicians correctly interpreted the rule in 96 % of cases , and the k value for interpretation was 0.77 ( 95 % CI , 0.65 to 0.89 ) . The potential relative reduction in use of radiography was estimated to be 28 % . The probability of fracture , if the decision rule were " negative , " is estimated to be 0 % ( 95 % CI , 0 % to 0.4 % ) . Attempts to refine the rule led to a model with improved specificity but with an unacceptable loss of sensitivity . CONCLUSION Prospect i ve validation has shown this decision rule to be 100 % sensitive for identifying fractures of the knee , to be reliable and acceptable , and to have the potential to allow physicians to reduce the use of radiography in patients with acute knee injury Abstract . Our objective was to determine the value of the Ottawa knee rules when applied by users with different levels of clinical training . We used a prospect i ve patient survey by the medical students and surgery residents of a European university trauma centre . The study group consisted of 261 eligible patients who presented with acute knee trauma during a 6-month period .  Radiography or  follow-up  was obtained for each patient . Data were separately analysed according to the degree of qualification of the initial examiner . The Ottawa knee rules had a sensitivity and a negative predictive value of 1.00 . Variable degree of medical competence of the users did not alter the accuracy of the rules . Application of the rules would have reduced knee radiography requests by 25 % . The Ottawa knee rules remain highly sensitive when applied by medical users with different levels of qualification , such as encountered in a teaching setting STUDY OBJECTIVE To derive a highly sensitive decision rule for the selective use of radiography in acute knee injuries . DESIGN Prospect ively administered survey . SETTING Emergency departments of two university hospitals . PARTICIPANTS Convenience sample of 1,047 adults with acute knee injuries . RESULTS Attending emergency physicians assessed each patient for 23 st and ardized clinical findings , which were recorded on data collection forms . A total of 127 patients was examined independently by two physicians to determine interobserver agreement . The outcome measure was fracture of the knee . Any patients who did not have ED radiography  underwent a  structured telephone interview  to determine the possibility of a missed fracture . Those variables found to be both reliable ( highest kappa values ) and strongly associated with a fracture ( highest chi 2 values ) were further analyzed by a recursive-partitioning multivariate technique . The derived decision rule included the following variables : ( 1 ) age 55 years or older , ( 2 ) tenderness at the head of the fibula , ( 3 ) isolated tenderness of the patella , ( 4 ) inability to flex to 90 degrees , and ( 5 ) inability to bear weight both immediately and in the ED ( four steps ) . The presence of one or more of these findings would have identified the 68 fractures in the study population with a sensitivity of 1.0 ( 95 % confidence interval [ Cl ] , .95 to 1.0 ) and a specificity of .54 ( 95 % Cl , .51 to .57 ) . Application of the rule would have led to a 28.0 % relative reduction in the use of radiography from 68.6 % to 49.4 % in the study population . CONCLUSION A practical , highly sensitive , and reliable decision rule for the use of radiography in acute knee injuries has been derived . Clinical application should await prospect i ve validation of the rule OBJECTIVES To study : 1 ) the efficiency of the current use of radiography in acute knee injuries , 2 ) the judgments and attitudes of experienced clinicians in their use of knee radiography , and 3 ) the potential for decision rules to improve efficiency . METHODS This two-stage study of adults with acute knee injuries involved : 1 ) a retrospective review of all 1,967 patients seen over a 12-month period in the EDs of one community and two teaching hospital , and 2 ) a prospect i ve survey of another 1,040 patients seen by attending emergency physicians . The prospect i ve survey assessed each clinician 's estimate of the probability of a knee or patella fracture ; 120 patients were independently assessed by two physicians . RESULTS Of the 1,967 patients seen in the first stage , 74.1 % underwent  radiography  but only 5.2 % were found to have fractures . Of the 1,727 knee and patella radiographic series ordered , 92.4 % were negative for fracture . In the second stage , experienced physicians predicted the probability of fracture to be 0 or 0.1 for 75.6 % of the patients . The kappa value for this response was 0.51 ( 95 % CI 0.34 to 0.68 ) . The physicians also indicated that they would have been comfortable or very comfortable in not ordering  radiography  for 55.5 % of the patients . The area under the receiver operating characteristics curve for the physicians ' prediction of fracture was 0.87 ( 95 % CI 0.82 to 0.91 ) , reflecting good discrimination between fracture and nonfracture cases . Likelihood ratios for the physicians ' prediction ranged from 0.09 at the 0 level to 42.9 at the 0.9 - 1.0 level . CONCLUSIONS Emergency physicians order radiography for most patients with acute knee injuries , even though they can accurately discriminate between fracture and nonfracture cases and expect most of the radiographs to be normal . These findings suggest great potential for more efficient use of knee radiography , possibly through the use of a clinical decision rule We design ed a prospect i ve observational study to attempt to vali date two recently described clinical decision rules for knee radiography .  Consecutive patients aged > or = 15 yr with acute knee injuries occurring less than 1 wk prior to presentation were included for study . Patients with distracting conditions , open knee injuries , or previous surgery were excluded . Each patient was assessed for 7 historical and 15 physical examination criteria that were recorded on a st and ardized data collection instrument . Radiographs were ordered at the discretion of the attending physician and were read by two board-certified radiologists . When radiographs were not ordered , structured telephone follow-up was performed after 3 wk . The main outcome parameter was the presence or absence of a clinical ly significant fracture . There were 351 patients in the study ; 26 ( 7 % ) had knee fractures . Fractures were significantly associated with an increased prevalence for two of the three criteria in the rule derived by Bauer : inability to weight bear immediately or in the emergency department ( ED ; 76.9 % of patients with a fracture vs. 29.8 % of patients without a fracture ) and effusion ( 53.8 % vs. 28.9 % , respectively ) . Ecchymosis was not significantly associated with fracture ( 19.2 % with fracture vs. 9 % with no fracture ) . Use of the Bauer rule would have led to a radiographic evaluation of 22 of the 26 patients with knee fractures ( sensitivity = 84.6 % , specificity = 48.9 % ) . Fractures were associated with a significantly increased prevalence for three of the five criteria in the decision rule proposed by Stiell : isolated patella tenderness ( 30.8 % with fracture vs. 14.5 % with no fracture ) , inability to flex the knee to 90 degrees ( 42.3 % vs. 19.7 % , respectively ) , and inability to weight bear immediately and in the ED ( 57.7 % vs. 18.8 % , respectively ) . Age > or = 55 yr ( 23.1 % vs. 12.0 % , respectively ) and fibula head tenderness ( 11.5 % vs. 5.5 % , respectively ) were not significantly associated with fracture . Use of the Stiell rule would have led to radiographic evaluation of 22 of the 26 patients with knee fractures ( sensitivity = 84.6 % , specificity = 49.8 % ) . We conclude that neither clinical decision rule is 100 % sensitive . Further refinement will be necessary to identify all patients with knee fractures CONTEXT The Ottawa Knee Rule is a previously vali date d clinical decision rule that was developed to allow physicians to be more selective and efficient in their use of plain radiography for patients with acute knee injuries . OBJECTIVE To assess the impact on clinical practice of implementing the Ottawa Knee Rule . DESIGN Controlled clinical trial with before-after and concurrent controls . SETTING Emergency departments of 2 teaching and 2 community hospitals . PATIENTS All 3907 consecutive eligible adults seen with acute knee injuries during two 12-month periods before and after the intervention . INTERVENTION During the after period in the 2 intervention hospitals , the Ottawa Knee Rule was taught to all house staff and attending physicians who were encouraged to order knee radiography according to the rule . MAIN OUTCOME MEASURES Referral for knee radiography , accuracy and reliability of the rule , mean time in emergency department , and mean charges . RESULTS There was a relative reduction of 2 
    Output:
    
Application of the OKR can rule out knee fracture and thus avoid unnecessary radiography .
These results also translate to improved efficiency , lower medical costs and reduced waiting times .
• The Ottawa Knee Rule helps clinicians to rule out fracture in adults with an acute knee injury .
• The rule allows a reduction in radiography requests , patient waiting time in the emergency department and healthcare costs