Ottawa Ankle Rules Calculator

Apply the Ottawa Ankle and Foot Rules to determine whether ankle or midfoot radiography is indicated after an acute injury — a highly sensitive rule for excluding clinically significant fracture.

🦵 Decision Rule📐 X-ray indicated if any listed criterion is positive🏥 Health
Bone tenderness at posterior edge or tip of lateral malleolus
Bone tenderness at posterior edge or tip of medial malleolus
Bone tenderness at base of 5th metatarsal
Bone tenderness at navicular
Unable to bear weight 4 steps immediately and in the assessment room
Please enter valid values.

Formula & Reference

VariableSymbolFormulaUnits
Ottawa Ankle Rules Calculator—X-ray indicated if any listed criterion is positiveyes / no

Step-by-Step Examples

Example 1
Negative Rule

Inversion injury. No malleolar tenderness, no midfoot tenderness, walked four steps in the department.

  • All five criteria negative
  • Neither ankle nor foot series triggered
✓ No imaging indicated by the rule
Example 2
Ankle Series Indicated

Tenderness at the tip of the lateral malleolus, able to bear weight, no midfoot tenderness.

  • Lateral malleolus tenderness → positive
  • Ankle criteria satisfied
  • Foot criteria not met
✓ Ankle X-ray series indicated
Example 3
Both Series Indicated

Unable to take four steps, tenderness at both the medial malleolus and the base of the fifth metatarsal.

  • Inability to bear weight triggers both rules
  • Medial malleolus tenderness → ankle series
  • 5th metatarsal tenderness → foot series
✓ Ankle and foot series indicated

Real-World Applications

🚑
Emergency Department Imaging
The Ottawa rules substantially reduce unnecessary ankle radiographs without missing clinically significant fractures.
☢️
Radiation Reduction
Fewer unnecessary X-rays means less cumulative radiation exposure, particularly valuable in younger patients.
⏱️
Reduced Waiting Times
Avoiding low-yield imaging shortens emergency department length of stay for patients with simple sprains.
📚
Evidence-Based Practice Teaching
The Ottawa rules are the textbook example of a well-derived, well-validated, and widely implemented clinical decision rule.

Common Mistakes to Avoid

⚠️
Palpating the wrong part of the malleolus

The rule specifies the posterior edge or tip over a 6 cm distance. Tenderness over the anterior ligaments indicates sprain, not fracture, and does not count.

⚠️
Applying the rule to old injuries

Validation was in acute injuries, generally within 10 days. Applying it to chronic pain gives an unvalidated result.

⚠️
Using it in excluded populations

The rules are not validated in children under 5, in patients with intoxication, altered sensation, distracting injuries, or gross swelling that prevents reliable palpation.

Frequently Asked Questions

What are the Ottawa Ankle Rules? ▾
A validated decision rule specifying that ankle radiographs are needed only with malleolar zone pain plus bone tenderness at either malleolus or inability to bear weight, with parallel criteria for the midfoot.
How accurate are they? ▾
Pooled sensitivity for clinically significant fracture approaches 100% across many validation studies, which is why the rule is used to safely exclude rather than confirm fracture.
What does inability to bear weight mean exactly? ▾
Being unable to take four steps — two on each foot — both immediately after the injury and during the clinical assessment. Limping still counts as bearing weight.
Do the rules apply to children? ▾
They have been validated in children over roughly 5 years of age, but not in younger children where examination reliability is poorer.
Can I use this to decide whether to go to hospital? ▾
No. This is a clinician-facing rule applied during examination. If you have an injury you are worried about, seek medical assessment.

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