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Ottawa Knee Rule

Calculators  Musculoskeletal
The Ottawa Knee Rule determines if knee fracture could be safely rule out without the use of imaging.
Age ≥55
No 0
Yes 1
Isolated tenderness of the patella (no other bony tenderness)
No 0
Yes 1
Tenderness at the fibular head
No 0
Yes 1
Unable to flex knee to 90°
No 0
Yes 1
Unable to bear weight both immediately and in ED (4 steps, limping is okay)
No 0
Yes 1
Result:

Background

Measured Factor
The need for knee imaging because knee fracture cannot be ruled out.
Measured Factor Disease
  • Clinically significant knee fracture
Measured Factor Detail
The Ottawa Knee Rule determines if knee fracture could be safely rule out without the use of imaging in patients ≥ 2 year old presenting with acute knee injuries.  Application of this calculator reduces the use of unnecessary and costly radiography. The decision rule is based on criteria including age ≥ 55, isolated tenderness of the patella (no other bony tenderness), tenderness at the fibular head, inability to flex knee to 90 degrees, and inability to bear weight both immediately and in the emergency department (four steps). If patient meets any of these criteria, knee imaging is recommended.
Speciality
Emergency Medicine Physician
Body System
Musculoskeletal
Measured Factor High Impact
  • High risk for knee fracture. Knee imaging is recommended.

Result Interpretation

Ranges Ranges
  • Critical High: Scores ≥ 1: Knee imaging is recommended due to high risk for clinically significant knee fracture.
  • Normal: Score 0: Knee fracture is ruled out. Knee imaging is not indicated.
  • Normal Adult Male: Score 0: Knee fracture is ruled out. Knee imaging is not indicated.
  • Normal Adult Female: Score 0: Knee fracture is ruled out. Knee imaging is not indicated.
  • Normal Pediatric: Score 0: Knee fracture is ruled out. Knee imaging is not indicated.
  • Normal Geriatric Male: Score 0: Knee fracture is ruled out. Knee imaging is not indicated.
  • Normal Geriatric Female: Score 0: Knee fracture is ruled out. Knee imaging is not indicated.
Result High Conditions
  • Clinically significant knee fracture
Test Limitations
The Ottawa Knee Rule has low specificity (0.54) and low positive predictive value (0.13). The rule is not specific to rule in fractures.  If one or more of the criteria are met, imaging is recommended, or physician needs to use clinical judgement to determine if imaging is necessary.
References: 1

Studies

Study Validation 1
This cross-sectional study compared the diagnostic accuracy and reproducibility of the Ottawa Knee Rules and Pittsburgh Decision Rules. Ninety injuries from patients 18 years and older were included in the study. There were two observer groups: emergency medicine residents and surgical residents. Pooled sensitivity and specificity were compared using χ(2) statistics, and interobserver agreement was calculated by using κ statistics. The Ottawa Knee Rules has a pooled sensitivity and specificity of 0.86 and 0.51, respectively. The Pittsburgh Decision Rules had a pooled sensitivity and specificity of 0.86 and 0.51, respectively.  The Pittsburgh Decision Rules was significantly more specific than the Ottawa Knee Rules (P = .002). The κ values for the Ottawa Knee Rules and Pittsburgh Decision Rules were 0.51 and 0.71, respectively. In conclusion, the Pittsburgh Decision Rules is more specific than the Ottawa Knee Rules, even though they have equal sensitivity.
References: 2
Study Validation 2
This prospective cohort study validated the Ottawa Knee Rule when applied to 283 Iranian patients with acute knee injury at the Imam Hospital Emergency Department. The decision rule had a sensitivity of 0.95 (95% confidence interval: 0.77 to 0.99), and a specificity of 0.44 (95% confidence interval: 0.37 to 0.50). The potential reduction in use of radiography was estimated to be 41%. The Ottawa Knee Rule missed only one fracture. The study concluded that the Ottawa Knee Rule is a highly sensitive for detecting knee fractures.
References: 3
Study Validation 3
This prospective and multicenter study determined the sensitivity and specificity of the Ottawa Knee Rule. A total of 750 children aged 2 to 16 years presented to the emergency department with knee injuries sustained in the preceding 7 days were enrolled. The Ottawa Knee Rules were 100% sensitive (95% confidence interval (CI): 94.9% to 100%), with a specificity of 42.8% (95% CI: 39.1% to 46.5%). Moreover, the Ottawa Knee Rule reduced 209 (31.2%) unnecessary radiographs. The study concluded that the Ottawa Knee Rule can be used in children with knee injuries and reduces the use of unnecessary radiography.
References: 4
Study Additional 1
This prospective cohort study assessed the ability of the Ottawa Knee Rule to correctly identify knee fractures.  Data from 1,522 patients at 11 hospitals of the Osakidetza-Basque Country Health Service were used. Emergency physicians applied the Ottawa Knee Rule to determine the need for radiography. Radiography was performed in all patients, regardless of the recommendation from Ottawa Knee Rule. The decision rule had a sensitivity of 1.0 (95% confidence interval (CI) 0.96 to 1.0). It identified 89 patients with clinically important fractures and reduced 49% of radiography use. In conclusion, the Ottawa Knee Rules is 100% sensitive and helps physicians reduce the use of unnecesary radiography.
References: 5
Study Additional 2
This prospective and consecutive study validated the Ottawa knee rule in 234 children aged 18 years or younger. These patients had acute traumatic knee injury of less than one week. The Ottawa knee rule identified 12 out of 13 patients with fractures (92% sensitivity; 95% confidence interval: 64%-99%). The missed case was an 8 year-old male who had sustained a nondisplaced fracture of the proximal tibia after a fall. Since the Ottawa knee rule did not identify all patients with knee fractures, the authors suggested to modify the rule to accommodate the differences between pediatric and adult patients in routine clinical practice.
References: 6

Authors

Ian Stiell, MD, MSc, FRCPC, is a senior scientist and a distinguished professor in the Department of Emergency Medicine at the University of Ottawa, Canada. He is also the editor-in-chief of the Canadian Journal of Emergency Medicine. His research focuses on clinical decision rules, acute heart failure, and atrial fibrillation.
https://med.uottawa.ca/emergency/people/stiell-ian

References

  1. Stiell IG, Greenberg GH, Wells GA, McKnight RD, Cwinn AA, Cacciotti T, et al. Derivation of a decision rule for the use of radiography in acute knee injuries. Ann Emerg Med. 1995 Oct;26(4):405-13.
  2. Cheung TC, Tank Y, Breederveld RS, Tuinebreijer WE, de Lange-de Klerk ES, Derksen RJ. Diagnostic accuracy and reproducibility of the Ottawa Knee Rule vs the Pittsburgh Decision Rule. Am J Emerg Med. 2013 Apr;31(4):641-5.
  3. Jalili M, Gharebaghi H. Validation of the Ottawa Knee Rule in Iran: a prospective study. Emerg Med J. 2010 Nov;27(11):849-51.
  4. Bulloch B, Neto G, Plint A, Lim R, Lidman P, Reed M, et al.; Pediatric Emergency Researchers of Canada. Validation of the Ottawa Knee Rule in children: a multicenter study. Ann Emerg Med. 2003 Jul;42(1):48-55.
  5. Emparanza JI, Aginaga JR; Estudio Multicéntro en Urgencias de Osakidetza: Reglas de Ottawa (EMUORO) Group. Validation of the Ottawa Knee Rules. Ann Emerg Med. 2001 Oct;38(4):364-8.
  6. Khine H, Dorfman DH, Avner JR. Applicability of Ottawa knee rule for knee injury in children. Pediatr Emerg Care. 2001 Dec;17(6):401-4.