What Is the Ottawa Ankle Rule? A Clinician's Quick Reference
The Ottawa Ankle Rule is one of the most elegant decision tools in medicine: three criteria, 99%+ sensitivity, and the ability to cut unnecessary ankle x-rays by 30–40%. If you're heading into clinical rotations or board prep, this one belongs in permanent memory.
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Evidence-based · For exam prep, not medical advice
update Updated October 2026
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Built by surgery and anesthesiology residents·Written for USMLE Step 1
bolt The 60-second version
check_circleApply to patients ≥18 with ankle injury within 10 days
check_circleTenderness: posterior edge/tip of lateral OR medial malleolus (distal 6 cm each)
check_circleOr: inability to weight-bear 4 steps immediately AND in the ED
check_circle~99.3% sensitivity for clinically significant fractures
check_circleNOT valid in children <18, pregnancy, intoxication, or distracting injuries
The Three Criteria
X-ray the ankle ONLY if there is pain in the malleolar zone AND any of: (1) bone tenderness at the posterior edge or tip of the lateral malleolus (distal 6 cm), (2) bone tenderness at the posterior edge or tip of the medial malleolus (distal 6 cm), or (3) inability to weight-bear both immediately after injury AND in the ED (4 steps).
For the Foot (Ottawa Foot Rule)
X-ray the foot if there is pain in the midfoot zone AND any of: (1) bone tenderness at the base of the 5th metatarsal, (2) bone tenderness at the navicular, or (3) inability to weight-bear as described above. These are commonly tested together — know which landmarks apply to ankle vs. foot.
Sensitivity and Specificity
The Ottawa Ankle Rules have a sensitivity of ~99.3% for clinically significant fractures (meta-analyses across >15,000 patients). Specificity is lower (~30–40%), meaning false positives are common — the rules are designed to catch all fractures, not to eliminate all imaging. They reduce unnecessary x-rays by approximately 30–40%.
Clinical Pearls and Pitfalls
The rule is NOT valid in: children under 18 (separate pediatric criteria), pregnant patients, intoxicated patients, those with diminished sensation, isolated skin injuries, or multiple injuries distracting from the ankle assessment. Always reassess if the patient's pain changes. On boards, the question often tests whether you know the rule's limitations, not just its criteria.
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2 real questions on What Is the Ottawa Ankle Rule? A Clinician's Quick Reference
Straight from the Progress Note question bank, each with a cited explanation. No account needed.
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From our OITE bank
A patient with an ankle sprain has tenderness at the base of the fifth metatarsal. Which rule guides the need for foot radiographs?
Answer: A. The Ottawa ankle rules guide when to obtain ankle and foot radiographs after injury, including tenderness at the base of the fifth metatarsal for foot films. Validation studies show high sensitivity for excluding fractures. This is a common PGY-2 emergency/clinic algorithm.
A patient has lateral ankle pain after inversion injury and point tenderness over the distal fibula. Which clinical decision tool helps determine need for ankle radiographs?
Answer: B. The Ottawa Ankle Rules guide when to obtain ankle radiographs after injury to reduce unnecessary imaging. They rely on malleolar zone pain plus specific bony tenderness or inability to bear weight. Interns should know this tool for ED triage.
Source: Stiell IG, et al. Decision rules for the use of radiography in acute ankle injuries. JAMA. 1993 is appropriate OR use ACR Appropriateness Criteria 2020
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What is the sensitivity of the Ottawa Ankle Rule?expand_more
The Ottawa Ankle Rule has approximately 99.3% sensitivity for clinically significant ankle fractures across multiple large meta-analyses. Its specificity is lower (~30–40%), but it's designed as a screening tool — the priority is not missing fractures, not eliminating all imaging.
Does the Ottawa Ankle Rule apply to children?expand_more
No. The original Ottawa Ankle Rule was validated in adults (≥18 years). Children have open growth plates (physes) that can be injured without clear plain film findings, making the adult decision rule unreliable. Separate tools (like the Low Risk Ankle Rule) exist for pediatric patients.
What is the difference between the Ottawa Ankle Rule and the Ottawa Foot Rule?expand_more
They're often called together as the 'Ottawa Rules.' The Ankle Rule assesses the malleolar zone and uses malleolar tenderness landmarks. The Foot Rule assesses the midfoot zone using the base of the 5th metatarsal and navicular. Weight-bearing inability is shared criterion for both.
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