Ottawa knee rule

Trauma & imaging rules

Acute knee injury in adults. Any one finding means the rule calls for a knee x-ray.

What you enter

Age ≥55
Tenderness at the head of the fibula
Isolated tenderness of the patella (no other bone tenderness)
Unable to flex to 90°
Unable to bear weight both immediately and in the emergency department (4 steps)

FORMULAX-ray if any: age ≥55, fibular head tenderness, isolated patellar tenderness, unable to flex to 90°, unable to bear weight (4 steps) immediately and in the ED

SourceStiell IG et al. Derivation of a decision rule for the use of radiography in acute knee injuries. Ann Emerg Med 1995;26:405-13ReviewedFormula and thresholds checked against the source on 2026-09-28. If the source updates, this line will say so.