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EVIDENCE-TO-PRACTICE REVIEW  

 

67 
Copyright © by Indiana State University                                                                                Clinical Practice in Athletic Training  
All rights reserved. ISSN Online 2577-8188                                                                              Volume 6 – Issue 1 – April 2023 

 
 

Review of Diagnostic Accuracy of the Ottawa Knee Rules in Adult 
Acute Knee Injuries  
Sean L. Glover, MS, ATC*; Amy M. Loveless, MS, ATC†; Sara A. Posson MS, ATC‡; Zachary K. Winkelmann, PhD, SCAT, ATC 
*North Greenville University, Tigerville, SC; †George Washington University, Washington D.C.; ‡Texas A&M University – Corpus 
Christi, Corpus, Christi, TX; §University of South Carolina, Columbia, SC 
 

 
ABSTRACT 
Acute knee injuries are commonly found in athletic populations. The wide range of knee injuries can present a challenge deciding 
which injuries require imaging. Currently, radiography is considered the gold standard of imaging for knee fractures. However, 
imaging is often costly not only for the patient, but also for the healthcare system. Since imaging is expensive, it is critical that 
clinicians decipher which patients require such testing. The Ottawa Knee Rules (OKR) is a predictor tool created by Stiell et al in 
1995 to help clinicians accurately distinguish potential knee fractures from non-fractures for imaging purposes. The OKR guidelines 
state that a patient should be referred for radiography if he/she meets at least one of the following criteria: (1) 55+ years of age 
(2) tenderness over fibular head (3) secluded pain on the patella (4) cannot flex knee to 90 degrees (5) cannot bear weight for at 
least four steps. The OKR has been used in clinical settings to rule out knee fractures in patients. The ability of OKR to accurately 
differentiate knee fractures from non-fractures has been investigated to determine how effective the tool is. This article examined 
eight research studies including over 7,000 participants to determine the diagnostic accuracy of OKR in adults. This examination 
showed that OKR exhibited high accuracy in diagnosing knee fractures needing imaging. The OKR demonstrated a sensitivity of 
0.99, specificity of 0.49, LR+ of 1.86, and LR- of 0.07. This data indicates a confidence interval (CI) of 95%. Furthermore, OKR 
showed low risk of bias and was beneficial to reducing medical costs and medical wait times. More than half (5) of the studies 
indicated a reduction rate in imaging completed when utilizing OKR. Therefore, OKR is a beneficial and accurate tool to implement 
in clinical decision-making when making imaging referrals for acute knee injuries in adults. 
Content Focus: Health Care Competency  
 
Correspondence 
Dr. Zachary Winkelmann, 1300 Wheat Street, Columbia, SC 29208. 
E-mail: winkelz@mailbox.sc.edu   
Twitter: @zachwinkelmann  
 
Full Citation 
Glover SL, Loveless AM, Passon SA, Winkelmann ZK. Review of diagnostic accuracy of the Ottawa Knee Rule in adult acute 
knee injuries. Clin Pract Athl Train. 2023;6(1): 67-72. https://doi.org/10.31622/2023/0006.01.10.   
 

 
ORIGINAL REFERENCE 
Sims JI, Chau MT, Davies JR. Diagnostic accuracy of the Ottawa Knee Rule in adult acute knee 
injuries: A systematic review and meta-analysis. Emerg Radiol. (2020);30:4438-4446. doi: 
10.1007/s00330-020-06804-x. 

SUMMARY 
 
CLINICAL PROBLEM AND QUESTION 
 
Acute knee pain is a common complaint amongst the patients seen in emergency departments. Despite a high 
incidence of this, only a small number of cases are due to fractures.1 Plain radiography has minimal use in 
detecting injuries to soft-tissue structures in the knee such as muscular and ligamentous anatomy. In addition 
there is a significant financial burden for ordering radiographs in high volume.1 By performing an economic 
analysis of the effect of the Ottawa Knee Rules (OKR), it was reported that when used, there was a $3M 
USD dollar annual reduction in healthcare cost nationwide. The savings were found to be about a $34 USD 
per patient.2 Before the establishment of the OKR in 1995 by Stiell et al, there were no uniform methods to 
rule out knee fractures.1 Currently, the suggestion to refer for imaging due to a potential knee fracture 
includes one or more the following criteria: inability to bear weight after injury (regardless of limp), injury 

mailto:winkelz@mailbox.sc.edu
https://doi.org/10.31622/2023/0006.01.10


Review of Diagnostic Accuracy of the Ottawa Knee Rule in Adult Acute Knee Injuries 

 

68 
Copyright © by Indiana State University                                                                                Clinical Practice in Athletic Training  
All rights reserved. ISSN Online 2577-8188                                                                              Volume 6 – Issue 1 – April 2023 
  

to the patella specifically, tenderness over the fibular head, inability to achieve 90° of knee flexion, and 
any patient older than 55 years old.1-4 Leading up to this study there are no systematic reviews or meta-
analyses regarding the accuracy of the OKR in the adult population only.1 To prevent the ordering of 
unnecessary radiographs and cut down on costs, there is a need for a clinical decision aide to enable health 
care professionals to predict the presence of a knee fracture prior to an emergency department visit. 
Therefore, the purpose of this article was to examine the accuracy of the OKR in clinical settings.  

SUMMARY OF LITERATURE 

The databases Embase (Elsevier), MEDLINE, PubMed, and Scopus were searched to gather articles to include 
in the systematic review and meta-analysis. The criteria for articles included was original works where the 
OKR was utilized by physicians in emergency settings to diagnose the presence of acute knee injuries. Acute 
knee injuries were defined as the timespan of the first seven days after the initial trauma.2 To begin the 
process, abstracts were first manually screened by two reviewers to determine the potential eligibility of 
each article. Once eligible articles were established, complete reading took place. Upon final evaluation, 
the articles from 1995 to present that provided sufficient data about the diagnostic accuracy of OKR in 
adults were used. Each study within the articles included a follow-up radiography report to confirm the 
presence of a fracture. Articles looking at the accuracy of the OKR in pediatric patients were excluded. 
After the initial search, 116 articles were found. There were 54 duplicate articles and after screening, 8 
articles were deemed eligible and included in the study.  

SUMMARY OF INTERVENTIONS 

The Ottawa Knee Rules are intended to help clinicians accurately distinguish when to refer a potential knee 
fracture for imaging using the criteria found in Figure 1.1  

SUMMARY OF OUTCOMES 

Eight studies were enrolled in the meta-analysis, which involved a total of 7,385 adult patients. The patient 
and study characteristics included a patient age range of 18 to 101, seven prospective studies, one 
controlled clinical trial, and only two patients identifying as false-negative diagnoses. The QUADAS-2 tool 
identified most studies presented with a low risk of bias and concern regarding applicability. Several studies 
stood out in terms of presenting bias. One study presented with a high risk of bias for patient selection, while 
a different study presented with a risk of bias to the “flow and timing” criterion.5,6  Another study 
demonstrated bias related to the reference test. This is because the radiographs were read by both the 
physician and traumatologist.7 However, the gold standard for the radiograph is to be interpreted by the 
radiologist alone.7 Heterogeneity, a random effects model, between the eight studies was examined by the 
calculation of I^2 statistic, as well as, a bivariate random effects meta-analysis to calculate sensitivity, 
specificity, LR(+), and LR(-). Spearman’s rank correlation test and Begg’s test for publication bias were also 
calculated. 

FINDINGS AND CLINICAL IMPLICATIONS 

The meta-analysis demonstrates that there is a strong ability to rule out knee fractures using the OKR for 
adults who sustain acute knee injuries.  The rule was derived from Stiell et al, and was validated and 
implemented over 2 years, yielding a 1.0 sensitivity and negative predictive value in all trials that were 
conducted.6,8 The analysis of eight studies exploring 7385 adult patients demonstrated a high diagnostic 



Review of Diagnostic Accuracy of the Ottawa Knee Rule in Adult Acute Knee Injuries 

 

69 
Copyright © by Indiana State University                                                                                Clinical Practice in Athletic Training  
All rights reserved. ISSN Online 2577-8188                                                                              Volume 6 – Issue 1 – April 2023 
  

performance of OKR with a pooled sensitivity of 0.99 (95% CI, 0.97-1.00) and specificity of 0.49 (95% CI, 
0.47-0.51). A pooled LR+ of 1.86 (95% CI, 1.72-2.01), LR- of 0.07 (95% CI, 0.02-0.24) and DOR of 25.10 
indicated that a positive OKR increased the odds of having a knee fracture twofold, whereas the odds 
decreased by 99.03% given a negative OKR. Furthermore, a moderate non-significant heterogeneity 
sensitivity range of 0.86-1.0 and a high significant heterogeneity specificity range of 0.23-0.54 were 
calculated.  This means that there was low variability between the eight studies for sensitivity and high 
variability between the eight studies for specificity (I2 = 27.6%; I2 = 79.3% respectively). Table 1 provides 
the full results. Spearman’s rank correlation test demonstrated that there was no evidence of a threshold 
effect. Begg’s test for publication bias was moderate with a p value of 0.805. This means that there was 
moderate association between the eight studies used in this meta-analysis and moderate risk of bias.  

 
However, within the eight studies, it was unclear whether there was a need for further imaging giving a 
negative result on radiograph. According to the American College of Radiology Appropriateness Criteria, 
evidence-based guidelines for specific clinical conditions that are reviewed every three years by a 
multidisciplinary panel, both magnetic resonance (MR) and computerized tomography (CT) imaging are not 
recommended for acute knee injuries unless significant trauma or dislocation is observed.9  Although insurance 
may influence which tests are performed based on coverage and the sequency of testing, MR and CT imaging 
should not be dismissed when evaluating an acute knee injury because CT shows high accuracy in diagnosing 

Table 1. Results from Original Studies 

Study Authors 
Participants Country Results Clinical 

Significance 
Overall 
Risk of 

Bias 

Atkinson et al.10 130 England Sensitivity: 1.00 
Specificity: 0.54 

N/A Very Low 

Cheung et al.14 90 Netherlands Sensitivity: 0.86 
Specificity: 0.23 

N/A Very Low 

Emparanza et al.7 1522 Spain Sensitivity: 1.00 
Specificity: 0.52 

49% RR Low 

Jalili and 
Gharebaghi11 

283 Iran Sensitivity: 0.95 
Specificity: 0.44 

41% RR Low 

Ketelslegers et al.5 261 Belgium Sensitivity: 1.00 
Specificity: 0.43 

25% RR Low 

Stiell et al.8 1096 Canada Sensitivity: 1.00 
Specificity: 0.49 

28% RR Very Low 

Stiell et al.6 3907 Canada Sensitivity: 1.00 
Specificity: 0.48 

26.4% RR Moderate 

Szucs et al.4 96 United 
States 

Sensitivity: 1.00 
Specificity: 0.47 

N/A Low 

*RR - estimated reduction rate 



Review of Diagnostic Accuracy of the Ottawa Knee Rule in Adult Acute Knee Injuries 

 

70 
Copyright © by Indiana State University                                                                                Clinical Practice in Athletic Training  
All rights reserved. ISSN Online 2577-8188                                                                              Volume 6 – Issue 1 – April 2023 
  

occult and tibial plateau fractures, while the MR also plays an important role in the diagnoses of soft tissue 
pathologies.9 Although further radiography may be needed, this review showed that five of the eight studies 
produced a reduction of 26.4%-49% in radiography when using OKR.%. 

CLINICAL BOTTOM LINE 

It is important for clinicians to understand the most accurate tools to use in the evaluation and diagnostic 
processes of their practice. This allows a clinician to operate in their settings in the most efficient and practical 
manner. The OKR is a beneficial tool that can be used to rule out knee fractures in patients which prevents 
futile imaging from taking place. Based on the results of this study, OKR demonstrated an impressive ability 
to accurately rule out knee fractures. The OKR had a 0.99 sensitivity indicating that utilizing these guidelines 
has a significantly high capability of correctly identifying those who do not need imaging and the ability to 
rule out an acute knee fracture.10 Furthermore, OKR has exhibited high consistency between examiners, 
meaning multiple examiners are able to obtain the same results as each other when utilizing this tool.2 

Accurately identifying those who may have a knee fracture from those who do not is vital to appropriately 
referring patients for imaging only when necessary to reduce healthcare costs. As previously mentioned, use 
of the OKR can save $34 USD per patient and $3M USD annually in healthcare costs.2 With fewer people 
going to medical facilities, such as hospitals and urgent care, the time a person spends waiting to be seen 
decreases as a result.5,11 This allows people who absolutely need medical care to be seen and treated more 
quickly. Diagnostic tools are extremely useful for athletic trainers, physical therapists, and other healthcare 
professionals to use in clinical settings. One such tool, OKR, is a quick, easy, and costless tool that can be 
used in a clinic or on-field examination to determine if a patient needs imaging for a knee fracture. The OKR 
has demonstrated high accuracy when identifying those who do not have a knee fractures a highly accurate 
tool to use to minimize the number of unnecessary imaging, reduce costs, and limit the amount of time spent 
waiting in medical facilities.12-14 Therefore, it is beneficial for clinicians to apply OKR in their evaluation 
processes to reduce needless imaging, reduce medical costs, and decrease the time spent waiting in medical 
facilities.  

REFERENCES  

1. Sims JI, Chau MT, Davies JR. Diagnostic accuracy of the Ottawa Knee Rule in adult acute knee injuries: 
a systematic review and meta-analysis. Eur Radiol. 2020;30(8):4438-4446. 
https://doi.org/10.1007/s00330-020-06804-x.  

2. Beutel BG, Trehan SK, Shalvoy RM. The Ottawa knee rule: examining use in an academic emergency 
department. West J Emerg Med. 2012;13(4):366-372. 
https://doi.org/10.5811%2Fwestjem.2012.2.6892.  

3. Sims JI, Chau M, Davies J. Validation of the Ottawa knee rule in adults: A single centre study. J Med 
Radiat Sci. 2020;67(3):193-198. https://doi.org/10.1002/jmrs.411.  

4. Szucs PA, Richman PB, Mandell M. Triage nurse application of the Ottawa knee rule. Acad Emerg Med. 
2001;8(2):112-116. https://doi.org/10.1111/j.1553-2712.2001.tb01274.x.  

5. Ketelslegers E, Collard X, Vande Berg B, et al. Validation of the Ottawa knee rules in an emergency 
teaching centre. Eur Radiol. 2002;12(5):1218-1220. https://doi.org/10.1007/s00330-001-1198-9.  

6. Stiell IG, Wells GA, Hoag RH, et al. Implementation of the Ottawa Knee Rule for the use of 
radiography in acute knee injuries. JAMA. 1997;278(23):2075-2079. 

https://doi.org/10.1007/s00330-020-06804-x
https://doi.org/10.5811%2Fwestjem.2012.2.6892
https://doi.org/10.1002/jmrs.411
https://doi.org/10.1111/j.1553-2712.2001.tb01274.x
https://doi.org/10.1007/s00330-001-1198-9


Review of Diagnostic Accuracy of the Ottawa Knee Rule in Adult Acute Knee Injuries 

 

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Copyright © by Indiana State University                                                                                Clinical Practice in Athletic Training  
All rights reserved. ISSN Online 2577-8188                                                                              Volume 6 – Issue 1 – April 2023 
  

7. Emparanza JI, Aginaga JR, Estudio Multicentro en Urgencias de Osakidetza: Reglas de Ottawa G. 
Validation of the Ottawa Knee Rules. Ann Emerg Med. 2001;38(4):364-368. 
https://doi.org/10.1067/mem.2001.118011.  

8. Stiell IG, Greenberg GH, Wells GA, et al. Prospective validation of a decision rule for the use of 
radiography in acute knee injuries. JAMA. 1996;275(8):611-615. 

9. Tuite MJ, Kransdorf MJ, Beaman FD, et al. ACR Appropriateness Criteria Acute Trauma to the Knee. J 
Am Coll Radiol. 2015;12(11):1164-1172. https://doi.org/10.1016/j.jacr.2015.08.014.  

10. Atkinson P, Boyle A, Chisholm E. X-ray requesting patterns before and after introduction of the Ottawa 
Knee Rules in a UK emergency department. Eur J Emerg Med. 2004(11):207-207. 
https://doi.org/10.1097/01.mej.0000136697.49343.c6.  

11. Jalili M, Gharebaghi H. Validation of the Ottawa Knee Rule in Iran: a prospective study. Emerg Med J. 
2010;27(11):849-851. https://doi.org/10.1136/emj.2009.080267.  

12. Yao K, Haque T. The Ottawa knee rules - a useful clinical decision tool. Aust Fam Physician. 
2012;41(4):223-224. 

13. Vijayasankar D, Boyle AA, Atkinson P. Can the Ottawa knee rule be applied to children? A systematic 
review and meta-analysis of observational studies. Emerg Med J. 2009(26):250-253. 
https://doi.org/10.1136/emj.2008.063131.  

14. 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;31(4):641-645. https://doi.org/10.1016/j.ajem.2012.11.003.  

 

  

https://doi.org/10.1067/mem.2001.118011
https://doi.org/10.1016/j.jacr.2015.08.014
https://doi.org/10.1097/01.mej.0000136697.49343.c6
https://doi.org/10.1136/emj.2009.080267
https://doi.org/10.1136/emj.2008.063131
https://doi.org/10.1016/j.ajem.2012.11.003


The Ottawa Knee Rules
A predictor tool to help clinician decision-making

when making imaging referrals for acute knee
injuries in adults

A patient should be referred to radiography if they
meet at least one of the following criteria:

Inability to
flex to 90
degrees

Tenderness
over the
fibular

head (B)

55+
years of

age

Isolated
pain over

the patella
(A)

Inability to
weight bear
immediately

after and in the
emergency

department (at
least 4 steps)

https://piktochart.com/?utm_source=dynamic&utm_medium=watermark

	ABSTRACT



