Ottawa ankle rules calculator (ankle and foot X-ray)
Apply the Ottawa ankle rules to an acute ankle injury: pain in the malleolar or midfoot zone, bone tenderness at four set points and the 4-step weight-bearing test decide whether an ankle X-ray series, a foot X-ray series, both or neither is needed.
Guides
- Ottawa ankle rules in children: age limits and accuracyDo the Ottawa ankle rules work in children? What the pediatric studies found, the age they hold from, growth-plate fractures and X-rays saved.
How this Ottawa ankle rules calculator works
This Ottawa ankle rules calculator applies the refined rules that Stiell and colleagues published in JAMA in 1993, after deriving a first version from 750 adults in two university hospital emergency departments in 1992. The Ottawa ankle rules are a decision rule, not a points score: they split an ankle injury into two zones and ask whether any one finding is present in each. An ankle X-ray series is needed only if there is pain in the malleolar zone and any of three findings: bone tenderness at the posterior edge or tip of the lateral malleolus, bone tenderness at the posterior edge or tip of the medial malleolus, or inability to bear weight both immediately after the injury and in the emergency department. A foot X-ray series is needed only if there is pain in the midfoot zone and bone tenderness at the base of the fifth metatarsal, at the navicular, or the same inability to bear weight.
Ankle X-ray series = pain in the malleolar zone AND (lateral malleolus tenderness OR medial malleolus tenderness OR unable to bear weight)
Foot X-ray series = pain in the midfoot zone AND (fifth metatarsal base tenderness OR navicular tenderness OR unable to bear weight)
Unable to bear weight = unable to take 4 steps, both immediately after the injury and at the time of the examination
Each zone is judged on its own, so one patient can need an ankle series, a foot series, both or neither. The inability to bear weight counts in either zone that hurts. As the rule is usually taught, 4 steps means transferring weight twice onto each foot, and a limp still counts as bearing weight. Tenderness means pain when the examiner presses directly on bone at the named point, not soft-tissue pain over the ligaments. The 1992 version also used age 55 or over; the refined 1993 rules dropped age.
Ottawa ankle rules results and what they mean
An Ottawa ankle rules result tells you which of two standard X-ray series the rules call for, and its strength is ruling fractures out rather than in. In the second stage of Stiell's 1993 JAMA study, 453 adults were assessed with the refined rules: sensitivity was 1.0 for 50 malleolar zone fractures (95% CI 0.93 to 1.0) and 1.0 for 19 midfoot zone fractures (95% CI 0.83 to 1.0). The estimated probability of a fracture when the rule was negative was 0% (95% CI 0% to 0.8%) for the ankle series and 0% (0% to 0.4%) for the foot series, and the potential reduction in radiography was 34% for the ankle and 30% for the foot. A 2003 BMJ systematic review by Bachmann and colleagues pooled 27 studies with 15,581 patients and found a negative likelihood ratio of 0.08 for both the ankle and the midfoot, which at a 15% fracture prevalence leaves under 1.4% probability of fracture.
| Result | Findings | What the rules say |
|---|---|---|
| No X-ray series | No zone pain, or zone pain without any of the bone tenderness points or the 4-step test | The rules do not call for radiography. In the 1993 validation no fracture was missed with a negative rule. |
| Ankle X-ray series | Malleolar zone pain with lateral or medial malleolus tenderness, or unable to take 4 steps | Ankle series indicated. Most patients with a positive rule have no fracture: specificity in the reviewed studies ranged from 10% to 79%. |
| Foot X-ray series | Midfoot zone pain with fifth metatarsal base or navicular tenderness, or unable to take 4 steps | Foot series indicated. |
| Ankle and foot series | Both zones meet the rule | Both series indicated. |
In practice, the 1994 implementation trial at a university hospital cut ankle radiography by 28% and foot radiography by 14% relative to before, while use rose at a control hospital. Patients discharged without radiography spent less time in the department (80 vs 116 minutes) and were as satisfied with care (95% vs 96%), and no fractures were missed: sensitivity was 1.0 for 74 malleolar and 19 midfoot fractures.
When the Ottawa ankle rules are less reliable
The Ottawa ankle rules are less reliable when the examination they depend on cannot be trusted. The rules were derived and validated in adults with acute blunt ankle injuries, assessed by emergency physicians, so they assume a patient who can feel and report bone tenderness and who can try to walk. Their specificity is modest: Bachmann's review found it ranged from 10% to 79% across studies, so a positive rule leads to many normal films. Agreement between doctors was moderate in the 1993 study, with kappa values of 0.56 for the ankle series rule and 0.69 for the foot series rule when 116 patients were assessed with the original rules. The rules only decide whether an ankle or foot series is needed; they say nothing about ligament injury, and the 1992 derivation counted only clinically significant fractures. In children, Dowling's 2009 meta-analysis found the rules reliable over 5 years of age, and Plint's 1999 study found results that differed between the two hospitals.
For more on age, growth-plate injuries and the evidence in children, see the guide to the Ottawa ankle rules in children.
Questions
What are the Ottawa ankle rules?
A decision rule from Stiell and colleagues (1992, refined 1993) that decides whether an acute ankle injury needs an ankle X-ray series, a foot X-ray series, both or neither, from zone pain, bone tenderness at four points and the 4-step weight-bearing test.
What counts as unable to bear weight?
Being unable to take 4 steps both immediately after the injury and at the examination. As the rule is taught, 4 steps means weight goes onto each foot twice, and limping still counts as bearing weight.
Is there a separate Ottawa foot rule?
The midfoot part of the Ottawa ankle rules is often called the Ottawa foot rule. It calls for a foot X-ray series when there is midfoot zone pain with tenderness at the base of the fifth metatarsal or the navicular, or inability to bear weight.
Can the Ottawa ankle rules be used in children?
A 2009 meta-analysis of 12 studies and 3,130 children pooled a sensitivity of 98.5% and found the rules reliable over 5 years of age. See Ottawa ankle rules in children.
Is my data sent anywhere?
No. The rule runs in your browser, and what you tick is not sent or stored.
Sources
- Stiell IG, Greenberg GH, McKnight RD, Nair RC, McDowell I, Worthington JR. A study to develop clinical decision rules for the use of radiography in acute ankle injuries. Ann Emerg Med. 1992;21(4):384–390. doi:10.1016/s0196-0644(05)82656-3
- Stiell IG, Greenberg GH, McKnight RD, et al. Decision rules for the use of radiography in acute ankle injuries. Refinement and prospective validation. JAMA. 1993;269(9):1127–1132. doi:10.1001/jama.269.9.1127
- Stiell IG, McKnight RD, Greenberg GH, et al. Implementation of the Ottawa ankle rules. JAMA. 1994;271(11):827–832. doi:10.1001/jama.1994.03510350037034
- Bachmann LM, Kolb E, Koller MT, Steurer J, ter Riet G. Accuracy of Ottawa ankle rules to exclude fractures of the ankle and mid-foot: systematic review. BMJ. 2003;326(7386):417. doi:10.1136/bmj.326.7386.417
- Dowling S, Spooner CH, Liang Y, et al. Accuracy of Ottawa Ankle Rules to exclude fractures of the ankle and midfoot in children: a meta-analysis. Acad Emerg Med. 2009;16(4):277–287. doi:10.1111/j.1553-2712.2008.00333.x
- Plint AC, Bulloch B, Osmond MH, et al. Validation of the Ottawa Ankle Rules in children with ankle injuries. Acad Emerg Med. 1999;6(10):1005–1009. doi:10.1111/j.1553-2712.1999.tb01183.x