Ottawa Knee Rules

Decides whether a knee X-ray is needed after acute knee injury.

For healthcare professionals.These calculate a score or a measurement from values you enter. They do not diagnose, and they are no substitute for clinical judgement. If you are a patient, discuss any result with your own doctor rather than acting on it.

Age ≥ 55 years

Isolated tenderness of the patella (no other bone tenderness)

Tenderness at the head of the fibula

Inability to flex the knee to 90°

Unable to bear weight both immediately and in the ED (4 steps)

Result

X-ray Not Indicated

X-ray not indicated

No criteria present — knee X-ray can be safely omitted (sensitivity ~97-99% for clinically significant fracture).

Do not use when

Validated for ages ≥2 years; less applicable to isolated ligamentous-mechanism injuries without any of the above findings.

Source

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.

Shown for reference and checked against the source above. Confirm against current guidance before acting on it, and use your own clinical judgement.

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