Ottawa Ankle and Foot Rules Calculator (Do I Need an X-ray?)
Apply the Ottawa Ankle Rules after an ankle or foot injury — malleolar and midfoot pain, bone tenderness and the 4-step weight-bearing test — to see whether an ankle or foot X-ray series is indicated.
How it works
Ankle X-ray if malleolar-zone pain AND any of: tenderness at the posterior edge or tip of the lateral malleolus, the same at the medial malleolus, or inability to bear weight (4 steps) immediately and in the emergency department. Foot X-ray if midfoot-zone pain AND any of: tenderness at the base of the 5th metatarsal, tenderness at the navicular, or inability to bear weight.
The Ottawa Ankle Rules (Stiell et al., 1992–1993) are one of the best-validated clinical decision rules in emergency medicine. A systematic review of 27 studies found close to 100% sensitivity for ankle and midfoot fractures, so a negative result safely avoids an X-ray, cutting ankle radiographs by about 30–40%. The rules apply to adults and, in later studies, to children over about 6 years old; they are not meant for people who are intoxicated, have reduced sensation, multiple injuries or an injury more than 10 days old.
Worked example
After twisting her ankle playing football, a woman has pain around the ankle bones and tenderness at the tip of the outer ankle bone, but can walk four steps with a limp and has no midfoot pain: Recommendation — Ankle X-ray indicated; foot X-ray not indicated.
Sources: Stiell IG et al. Decision rules for the use of radiography in acute ankle injuries. JAMA 1993 · Bachmann LM et al. Accuracy of Ottawa ankle rules to exclude fractures of the ankle and mid-foot: systematic review. BMJ 2003
Frequently asked questions
Do I need an X-ray for a sprained ankle?
Under the Ottawa rules you need an ankle X-ray only if you have pain around the ankle bones plus tenderness at the back edge or tip of either ankle bone, or you could not take four steps both straight after the injury and when examined. Otherwise a fracture is very unlikely.
Does limping count as bearing weight?
Yes. Being able to transfer weight twice onto each foot (four steps) counts, even with a limp. Inability to bear weight means you could not take those four steps at all.
Can the Ottawa Ankle Rules be used in children?
Studies support them in children older than about 6, with similarly high sensitivity. In younger children and when growth plates are involved, clinical judgement matters more.
When should the rules not be used?
Not for people who are intoxicated, have head injuries, multiple painful injuries, reduced sensation in the legs, or injuries more than 10 days old — and never over a clinician’s suspicion of a fracture.
Related calculators
Clinical decision tool for education and for use by trained clinicians alongside clinical judgement — not a diagnosis and not a substitute for medical assessment. Scores validated in specific populations may not apply to every patient.