About the Ottawa Ankle Rules
The Ottawa ankle rules are a validated clinical decision rule for deciding which patients with an acute ankle injury need X-rays. Developed by Ian Stiell and colleagues at the University of Ottawa, refined and prospectively validated in JAMA in 1993, they were 100% sensitive for clinically significant malleolar and midfoot fractures in the validation study with an estimated potential reduction in radiography of 34% for ankle series and 30% for foot series. They are made up of an ankle series rule and a foot series rule.
This calculator is for emergency clinicians, urgent-care and sports medicine staff, physiotherapists and students. Record where the patient has pain, whether there is bone tenderness at the four key palpation points (posterior edge or tip of either malleolus, base of the fifth metatarsal, navicular), and whether they could bear weight for four steps both immediately after the injury and when examined. The tool tells you which X-ray series, if any, the rules indicate.
The rules were derived and validated in adults (18 and over) with acute blunt ankle injuries. They do not apply to patients who cannot be reliably examined — for example intoxication, head injury, multiple painful injuries or reduced sensation in the legs — or to pregnancy, isolated skin injuries, or injuries more than about 10 days old. Clinical judgement can always override a negative rule.
How to use the ottawa ankle rules
- 1Confirm the patient is an adult with an acute ankle injury who can be examined reliably.
- 2Ask where the pain is: malleolar zone, midfoot zone or both.
- 3Palpate the posterior edge and tip of both malleoli over the distal 6 cm.
- 4Palpate the base of the fifth metatarsal and the navicular bone.
- 5Ask whether they could take four steps right after the injury and observe them now.
- 6Read which X-ray series, if any, the rules indicate.
Formula and method
The Ottawa ankle rules are two "any-one-of" rules. An ankle radiograph series is indicated when there is pain in the malleolar zone plus any one of: bone tenderness along the distal 6 cm of the posterior edge or tip of the lateral malleolus, the same at the medial malleolus, or inability to bear weight both immediately and in the emergency department. A foot series is indicated when there is midfoot pain plus tenderness at the base of the fifth metatarsal or the navicular, or the same inability to bear weight.
Inability to bear weight means the patient cannot take four steps — two transfers of weight onto each foot — regardless of limping. Palpate the full distal 6 cm of the posterior edge of each malleolus, because tenderness only over the anterior ligaments suggests a sprain rather than a fracture.
Worked examples
Inversion sprain, walking, no bony tenderness
There is malleolar pain but no tenderness at either malleolus and the patient can bear weight, so neither rule is positive and X-rays are not indicated by the Ottawa rules.
Tender tip of the lateral malleolus
Malleolar pain plus bone tenderness at the posterior edge or tip of the lateral malleolus makes the ankle rule positive, so an ankle series is indicated.
Midfoot pain with tender fifth metatarsal base
Pain is in the midfoot zone and the base of the fifth metatarsal is tender — a classic site of avulsion fracture — so the foot rule calls for a foot series.
Unable to bear weight with ankle and midfoot pain
Inability to take four steps satisfies both rules when pain is present in both zones, so both ankle and foot series are indicated.
Frequently asked questions
How accurate are the Ottawa ankle rules?+
In the 1993 validation study the refined rules were 100% sensitive for malleolar and midfoot fractures. Systematic reviews since then report sensitivity close to 98–100%, with lower specificity, so a negative rule reliably rules out fracture.
What does unable to bear weight mean?+
It means the patient could not take four steps — two transfers onto each foot — both immediately after the injury and when examined. Limping counts as bearing weight if they manage the four steps.
Can the Ottawa ankle rules be used in children?+
The original rules were derived and validated in adults aged 18 and over. Later studies and meta-analyses have tested them in children, with good sensitivity in older children, but local paediatric guidance should be followed.
Where exactly should I press?+
Press along the posterior edge and tip of the lateral and medial malleoli over the distal 6 cm, the base of the fifth metatarsal on the outer foot, and the navicular on the inner midfoot.
When do the Ottawa ankle rules not apply?+
They should not be used for intoxicated patients, those with head injury or multiple painful injuries, reduced sensation in the legs, pregnancy, isolated skin injuries or injuries more than about 10 days old.
For healthcare professionals and education only. This calculator implements a published formula or score but is not a diagnosis and does not replace clinical judgment. Verify inputs and results against the original source before using them in patient care.