Emergency Medicine
Ottawa Ankle Rules
Whether ankle/foot X-rays are needed after injury.
Education and reference only. Not a substitute for clinical judgement, local policy or product labelling. Always verify before clinical use. Values are calculated in your browser and never stored.
Background
The Ottawa Ankle Rules are a validated decision tool that identifies which patients with an acute ankle or midfoot injury actually need an X-ray. An ankle X-ray is indicated for pain in the malleolar zone with bony tenderness at the posterior edge or tip of either malleolus, or inability to bear weight; a foot X-ray is indicated for midfoot pain with bony tenderness at the base of the fifth metatarsal or the navicular, or inability to bear weight. 'Unable to bear weight' means cannot take four steps both immediately after injury and during assessment. The rules are designed for high sensitivity, accepting some unnecessary imaging to avoid missing fractures.
Interpreting the result
If none of the criteria are present, a clinically significant fracture is very unlikely and imaging can usually be safely avoided. If one or more criteria are present, an X-ray of the relevant region (ankle or foot) is indicated. The rules are a screening tool to rule out fracture, not a guarantee, so persistent clinical concern can still justify imaging.
Advice
Ankle X-ray is indicated for malleolar-zone pain with malleolar tenderness or inability to weight-bear; foot X-ray for midfoot pain with 5th metatarsal/navicular tenderness or inability to weight-bear.
Worked example
A patient who twisted their ankle has tenderness over the tip of the lateral malleolus and could not walk four steps at the time or in the department. At least one criterion is present, so an ankle X-ray is indicated. Had they been tender only over soft tissue and able to weight-bear, imaging could have been avoided.
Pearls / pitfalls
- They apply to acute injuries; reliability falls with delayed presentation, intoxication, distracting injuries or impaired sensation.
- They were derived in adults but perform well in children over about five years, though local policy varies.
- Tenderness must be bony (over the malleolar edges, navicular or fifth metatarsal base) — diffuse soft-tissue tenderness does not count.
- A negative rule does not exclude ligamentous injury or every avulsion; safety-net advice and review for persistent symptoms still apply.
Evidence & validation
Derived and prospectively validated by Stiell and colleagues in the early 1990s, the rules have near-complete sensitivity for clinically significant fractures across many subsequent studies and meta-analyses. They reduce unnecessary radiography substantially and are endorsed in emergency-medicine practice internationally.
Frequently asked questions
When do the Ottawa Ankle Rules say no X-ray is needed?
When there is no bony malleolar tenderness, no fifth-metatarsal or navicular tenderness, and the patient can bear weight for four steps both immediately and during assessment. In that case a significant fracture is very unlikely.
What counts as inability to bear weight?
Being unable to take four steps (transferring weight onto each leg twice), both immediately after the injury and at the time of examination. Limping counts as bearing weight.
Do the rules cover the foot as well as the ankle?
Yes. Midfoot pain with tenderness at the base of the fifth metatarsal or navicular, or inability to weight-bear, indicates a foot X-ray, which is assessed separately from the ankle.
Can the rules be used in children?
They perform well in children over roughly five years of age in most studies, but apply local paediatric guidance, especially in very young children or where growth-plate injury is suspected.
Could a fracture still be missed if the rules are negative?
Rarely. The rules are highly sensitive but not perfect, so persistent pain or clinical concern warrants review or imaging despite a negative result.
References
- Stiell IG, Greenberg GH, McKnight RD, et al. Decision rules for the use of radiography in acute ankle injuries. JAMA. 1993;269(9):1127–1132.
- Royal College of Emergency Medicine. Ankle injury guidance / Ottawa Ankle Rules.
About the creator
Stiell IG et al.
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