Scores & indices
Ottawa ankle rules calculator
Two pain zones, four points of bony tenderness, four steps — and most ankle X-rays turn out to be unnecessary.
A patient who twisted an ankle at netball: pain in the malleolar zone with bony tenderness over the posterior edge of the lateral malleolus.
Ankle X-ray series indicated
Malleolar-zone pain plus malleolar bony tenderness meets the rule — this is the presentation where imaging earns its place, while the tender-nowhere, walking patient can safely skip it.
Who this is for
For emergency and primary-care clinicians examining an acute ankle or midfoot injury within 10 days. The rules work per zone: malleolar-zone pain asks about malleolar bony tenderness, midfoot pain asks about the fifth-metatarsal base and navicular, and inability to bear weight for four steps counts for both — safely ruling out the X-ray in most sprains, with 98–100% sensitivity for clinically significant fracture (Stiell 1992–1994).
How it works
What it does
Applies the Ottawa ankle and foot rules: for each pain zone, an X-ray is indicated only with the zone's bony tenderness findings or inability to bear weight for four steps.
Why trust it
Sensitivity for clinically significant fracture was 98–100% across large validation studies, with substantial reductions in unnecessary imaging. Applied properly, a negative rule is safer than a defensive X-ray habit.
When not to use it
Intoxication, distracting injuries, reduced leg sensation, and presentation more than 10 days after injury all undermine the examination; the rule is not validated under age 5. References: Stiell 1992–1994.
Built on published evidence
- Stiell et al. 1992 (derivation), 1993 (validation), 1994 (implementation)
Codification last reviewed 2026-08-28, and checked against published reference values in automated tests on every release — see the full evidence ledger.
Questions clinicians ask
How safe is skipping the X-ray when the rule is negative?
Sensitivity for clinically significant fracture was 98–100% across the large validation studies, with substantial reductions in unnecessary imaging — applied properly, a negative rule is safer than a defensive X-ray habit.
When should the rules not be applied?
Intoxication, distracting injuries, and reduced leg sensation all undermine the examination, the rules apply only within 10 days of injury, and they are not validated under age 5. Outside those conditions, examine and image on clinical judgement.
What counts as unable to bear weight?
Failing to take four steps — transferring weight twice onto each foot, limping allowed — both immediately after the injury and in the department. Managing four steps, however painfully, counts as weight-bearing.
Ankle series or foot series — which do I order?
It follows the zone: malleolar-zone pain with malleolar tenderness or inability to bear weight indicates an ankle series; midfoot pain with fifth-metatarsal-base or navicular tenderness, or inability to bear weight, indicates a foot series. Both zones can qualify in the same patient.
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