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SGEM#5: Does Johnny “kneed” an X-ray? (Ottawa Knee Rule)

SGEM#5: Does Johnny “kneed” an X-ray? (Ottawa Knee Rule)
Date: September 4, 2012

Case Scenario: Ten year old Johnny was playing hockey last night. Twisted his knee but could not finish the game. Mom brings him in after asking for an xray.

The Ottawa Knee Rule (OKR): These were also developed by Dr. Ian Stiell .The rule says xrays are only required if the patient has one or more of the following:

  1. Age 55 years or older
  2. Tenderness at head of fibula
  3. Isolated tenderness of patella
  4. Inability to flex to 90°
  5. Inability to bear weight both immediately and in the emergency department (4 steps)

(Does not apply to pregnant, drunk or head injured patients)

Dr. Stiell’s article on the OKR was published in the Ann Emerg Med 1995.  There were 127 patients in this prospective study. It showed application of the OKR was 100% sensitive and 54% specific. So it picked up all of the true positives or fractures. Applying the OKR would have decreased xrays by 28%.

Question: Can the Ottawa knee rules safely exclude knee fractures in children?

Reference: Vijayasankar D et al. Can the Ottawa knee rule be applied to children? A systematic review and meta-analysis of observational studies. Emerg Med J 2009

  • Population: 1130 children presenting to the ED with knee injuries. The prevalence of fracture in this group was 8.4%.
  • Intervention: Application of the Ottawa knee rule.
  • Control: None.
  • Outcome: Any fracture of the knee.

Authors’ Conclusions: “The available evidence suggests that the OKR can safely be applied to children over the age of 5 years. There is insufficient evidence to justify the use of the OKR in children less than 5 years.”

BEEM Commentary: The Ottawa Knee Rule has been well validated in adult patients and when used can safely reduce the number of radiographs required by these patients presenting with knee injuries. Although there have been some studies on the use of the Ottawa Knee rule in children, these studies have had relatively smaller numbers. This paper, for the first time, provides a meta-analysis of the available data. The systematic review did not include non-English papers, and thus may have excluded certain data-sets. The data presented is convincing that the Ottawa Knee Rule can safely be used in children over the age of 5 years. There was insufficient data to make conclusions about children less than 5 years.

BEEM Bottom Line: The Ottawa Knee Rule can be safely used in children over the age of 5 years.

Remember to be skeptical of anything you learn, even if you heard it on the Skeptics’ Guide to Emergency medicine.

  • Despite best evidence, some parents still come to the ED for an xray and will leave dis-satisfied without one

  • Ken

    Agree parents come with expectations. Just like providing Rx for viral URIs it can come down to communication. Yes it may add a little time to the visit but its worth the effort. Slowly community expectations can be changed.
    I will often raise the issue of radiation and “Primum non nocere”. It shows you care about their child and do not want to expose them to unnecessary radiation. Also can add that if it was my child…I would not get an xray.
    These strategies do not always work but it is worth trying. Let me know if you have any success.

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