Ottawa Ankle Rules Calculator
Ottawa ankle rules for ankle and foot X-rays after acute blunt ankle injury.
What it does
The Ottawa ankle rules are a clinical decision tool for adults with acute blunt ankle and midfoot injuries. They help decide whether ankle or foot radiography is needed.
An ankle series is indicated when there is pain in the malleolar zone plus bone tenderness at the posterior edge or tip of either malleolus, or inability to bear weight for four steps. A foot series is indicated when there is pain in the midfoot zone plus bone tenderness at the base of the fifth metatarsal or the navicular, or inability to bear weight.
The rules were designed to reduce unnecessary X-rays without missing clinically important fractures. They apply to patients who are awake, cooperative, and not intoxicated, and to injuries that are not more than 10 days old.
The defaults describe ankle pain with lateral malleolus tenderness and inability to bear weight. The ankle series is indicated, while the foot series is not. The tool suggests ordering only the indicated series and using clinical judgment for other injuries.
How to use
- Confirm that the injury is acute, blunt, and within 10 days.
- Ask about pain in the ankle and midfoot zones.
- Palpate the posterior edge and tip of both malleoli for bone tenderness.
- Palpate the base of the fifth metatarsal and the navicular.
- Assess whether the patient can bear weight for four steps.
- Press Calculate to see whether ankle or foot radiography is indicated.
Formula
- Ankle pain
- Pain in the malleolar zone.
- Malleolar tenderness
- Bone tenderness at the posterior edge or tip of either malleolus.
- Midfoot pain
- Pain in the midfoot zone.
- Midfoot tenderness
- Bone tenderness at the base of the fifth metatarsal or the navicular.
- Weight bearing
- Unable to take four steps at the time of injury and in the emergency department.
The rules use two parallel pathways. Ankle imaging needs ankle pain plus at least one ankle finding. Foot imaging needs midfoot pain plus at least one foot finding. Inability to bear weight applies to both pathways. The rules were validated for adults and are not a substitute for examining other injuries or for treating an open fracture, neurovascular deficit, or dislocated joint.
Worked example
Example: ankle pain, lateral tenderness, unable to bear weight
Defaults: ankle pain Yes, lateral malleolus tenderness Yes, medial tenderness No, midfoot pain No, fifth metatarsal tenderness No, navicular tenderness No, able to bear weight No.
- Ankle pain is present.
- Lateral malleolus tenderness is present, which satisfies an ankle finding.
- The patient is unable to bear weight, which also satisfies the ankle pathway.
- Midfoot pain is absent, so the foot pathway is not triggered.
- Ankle X-ray is indicated; foot X-ray is not.
- The tool suggests ordering only the indicated series.
Reference table
| Series | Indicated when |
|---|---|
| Ankle | Ankle pain plus bone tenderness at the posterior edge or tip of either malleolus, or inability to bear weight four steps |
| Foot | Midfoot pain plus bone tenderness at the base of the fifth metatarsal or navicular, or inability to bear weight four steps |
Limits
- The rules apply to adults with acute blunt injury within 10 days.
- They are not validated for children, pregnant patients, or people with impaired sensation.
- They do not apply to open fractures, obvious deformity, or neurovascular compromise.
- A negative rule does not replace reassessment if pain or function worsens.
Common mistakes
- Applying the rules to a chronic injury or a injury older than 10 days.
- Using tenderness over the Achilles tendon or other soft tissue as a positive bone finding.
- Counting weight bearing as normal when the patient needs assistance or cannot take four steps.
- Ordering both series when only one pathway is triggered.
- Using the rules in an intoxicated or uncooperative patient.
Try it yourself
Quick checks. Answers sit tucked under each question.
Ankle pain, medial tenderness, able to bear weight, no midfoot pain. Which X-ray is indicated?
Ankle X-ray. Ankle pain plus medial malleolus tenderness satisfies the ankle pathway.
Midfoot pain, navicular tenderness, able to bear weight, no ankle pain. Which X-ray is indicated?
Foot X-ray only. Midfoot pain plus navicular tenderness satisfies the foot pathway.
Ankle pain, no bone tenderness, unable to bear weight, no midfoot pain. Which X-ray is indicated?
Ankle X-ray. Inability to bear weight is an ankle criterion even without malleolar tenderness.
Questions
What do the Ottawa ankle rules do?
They identify adults with acute ankle or midfoot injury who need radiography, reducing unnecessary X-rays without missing important fractures.
Where exactly do I palpate?
The posterior edge and tip of the lateral and medial malleoli, the base of the fifth metatarsal, and the navicular bone.
What counts as unable to bear weight?
The patient cannot take four steps at the time of injury and in the emergency department, even with limping.
Can the rules be used in children?
The adult rules are not validated for children. A pediatric ankle rule or clinician judgment should be used instead.
Do the rules cover the knee or higher injuries?
No. They cover the ankle and midfoot. Other pain and tenderness need a separate assessment.
What if the patient has an obvious deformity?
Obvious deformity, open fracture, or neurovascular compromise needs urgent assessment and imaging regardless of the rule.