MAGENT

Ottawa ankle rules: the findings and how they combine

The Ottawa ankle rule combines up to five yes/no examination findings after an ankle injury: pain in the malleolar zone, bone tenderness at the lateral malleolus, bone tenderness at the medial malleolus, and inability to bear weight both right after the injury and at the time of examination. The rule is met when there is malleolar-zone pain plus at least one of the other findings, with the two weight-bearing findings counting together as one. Malleolar pain with tenderness at the tip of the lateral malleolus meets the rule; malleolar pain alone doesn't.

Not a medical device. Not a diagnosis or dosing recommendation.

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What are the Ottawa ankle rules?

The Ottawa ankle rules are a clinical decision rule developed by Ian Stiell and colleagues in Ottawa, Canada, and first published in 1992. They're built from a short physical examination of an injured ankle: where it hurts, whether specific points on the ankle bones are tender, and whether the person can walk.

They're also called the Ottawa ankle rule (singular), the Stiell ankle rule or OAR. The original work covered both the ankle and the midfoot; Magent's calculator handles the ankle part alone.

This page explains which findings go in and how they combine. It doesn't say what to do when the rule is met, and it doesn't diagnose a fracture.

The Ottawa ankle rule logic

rule met = malleolar_pain AND (
             lateral_malleolus_tenderness
          OR medial_malleolus_tenderness
          OR (unable_to_bear_weight_immediately AND unable_to_bear_weight_at_exam)
          )

Exact expression the calculator uses:

Ankle x-ray indicated iff malleolar_pain and (lateral_malleolus_tenderness or medial_malleolus_tenderness or (unable_to_bear_weight_immediately and unable_to_bear_weight_in_ed))

In words: there must be pain in the malleolar zone. Then the rule is met if either malleolus is tender at its posterior edge or tip, or if the person couldn't bear weight both immediately after the injury and at the examination.

What each part means

InputPlain-English meaningAnswer
malleolar_painPain in the malleolar zone, the area around the ankle bonesyes / no
lateral_malleolus_tendernessBone tenderness at the posterior edge or tip of the lateral malleolus (outer ankle bone)yes / no
medial_malleolus_tendernessBone tenderness at the posterior edge or tip of the medial malleolus (inner ankle bone)yes / no
unable_to_bear_weight_immediatelyCouldn't take four steps right after the injuryyes / no
unable_to_bear_weight_in_edCan't take four steps at the examination (in the emergency department)yes / no

How the logic works

  1. Start with malleolar pain. If there's no pain in the malleolar zone, the rule isn't met, whatever the other findings are.
  2. Check the lateral malleolus. Tenderness at its posterior edge or tip is enough.
  3. Check the medial malleolus. Tenderness at its posterior edge or tip is enough.
  4. Check weight bearing. This counts just when the person couldn't take four steps both right after the injury and at the examination. One without the other doesn't count.
  5. If step 1 is yes and any of steps 2–4 is yes, the rule is met.

Inputs are yes or no

Every input is true or false. There are no points to add up and no numbers to measure. The calculator doesn't examine the ankle; the person examining the patient answers the five questions. Magent's calculator returns true or false for the rule, plus a line for each finding showing whether it was met.

Worked examples

These use Magent's own expected values for the calculator.

Example 1: no findings

  1. No malleolar pain.
  2. Rule: not met.

Example 2: malleolar pain and lateral malleolus tenderness

  1. Malleolar pain: yes.
  2. Lateral malleolus tender at the posterior edge or tip: yes.
  3. Rule: met.

Example 3: malleolar pain and medial malleolus tenderness

  1. Malleolar pain: yes.
  2. Medial malleolus tender: yes.
  3. Rule: met.

Example 4: unable to bear weight right after the injury, but able at the examination

  1. Malleolar pain: yes.
  2. No malleolus tenderness.
  3. Weight bearing failed immediately but not at the examination, so the weight-bearing finding isn't met.
  4. Rule: not met.

Example 5: unable to bear weight both times

  1. Malleolar pain: yes.
  2. Couldn't take four steps immediately or at the examination.
  3. Rule: met.

Example 6: lateral tenderness but no malleolar pain

  1. Malleolar pain: no.
  2. Rule: not met, even though the lateral malleolus is tender.

Ottawa ankle rule reference values

These are Magent's expected values for the calculator. With no findings, the rule isn't met. Lateral malleolus tenderness without malleolar pain doesn't meet it, and neither does malleolar pain alone. Malleolar pain with lateral malleolus tenderness meets it, and so does malleolar pain with medial malleolus tenderness. Malleolar pain with inability to bear weight both immediately and at the examination meets it. Malleolar pain with inability to bear weight immediately but not at the examination, or at the examination but not immediately, doesn't.

History of the Ottawa ankle rules

The rule comes from Ian G. Stiell, Gary H. Greenberg, R. Douglas McKnight and colleagues, A study to develop clinical decision rules for the use of radiography in acute ankle injuries, published in Annals of Emergency Medicine in 1992 (volume 21, issue 4, pages 384–390).

The abstract describes a prospective study in two university hospital emergency departments: 155 adults in a pilot stage and 750 in the main study, all with acute blunt ankle injuries. Staff emergency physicians recorded 32 standardized clinical findings before any imaging, and the authors used statistical methods to build rules from them.

The 1992 rule also included age 55 or older as one of the findings. The version described in the BMJ study below doesn't include age, and that's the version Magent's calculator follows.[1]

When it's used

A 2009 study in the BMJ describes the Ottawa ankle rules as a clinical decision tool that aids the efficient use of radiography in acute ankle injuries.[1] Its version of the rule describes the tender area of each malleolus as the distal 6 cm.[1]

Where it's used

The same study calls the rules well known and widely used internationally.[1] It was carried out in the emergency departments of a tertiary teaching hospital and a community hospital in Australia, where the authors found the rules were either not being used or applied in varying ways.[1]

Who uses it

The 2009 study worked with emergency department staff and radiographers, using education sessions, a new request form built around the rules, posters and lanyard cards, audit and feedback, and radiographers checking request forms.[1]

Limits of the calculation

  • It combines five yes/no findings. It doesn't examine the ankle and doesn't diagnose a fracture.
  • It's the ankle rule. It isn't the Ottawa foot (midfoot) rule, which looks at the navicular bone and the base of the fifth metatarsal, and it isn't the Ottawa knee rule.
  • Weight bearing counts when it failed both immediately and at the examination, not one or the other.
  • The record describes it as the adult rule as published. The calculator doesn't take age.
  • This page doesn't say what to do when the rule is met.

Clinical decisions belong to a qualified clinician who knows the patient.

  • Ottawa knee rule uses age, fibular head tenderness, isolated kneecap tenderness, knee flexion and the same two-part weight-bearing test. It applies to knee injuries, not ankles.

Glossary

  • Malleolus: one of the two bony bumps at the ankle. The lateral malleolus is on the outside (the end of the fibula); the medial malleolus is on the inside (the end of the tibia).
  • Malleolar zone: the area around both malleoli.
  • Bone tenderness: pain when the examiner presses directly on the bone.
  • Bear weight: stand and walk on the injured leg; here, take four steps.
  • Midfoot: the middle of the foot, which has its own Ottawa foot rule.

Common mistakes

  • Counting one weight-bearing failure. It must be both immediately after the injury and at the examination.
  • Skipping malleolar pain. Without pain in the malleolar zone, the rule isn't met even if a malleolus is tender.
  • Pressing the front of the malleolus. The findings are at the posterior edge or the tip.
  • Using the ankle rule for a midfoot injury. That's the separate foot rule.

Source

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

Further reading

  1. Bessen T, Clark R, Shakib S, Hughes G. A multifaceted strategy for implementation of the Ottawa ankle rules in two emergency departments. BMJ. 2009;339:b3056.

Frequently asked questions

What are the Ottawa ankle rules?

A 1992 decision rule built from malleolar-zone pain, bone tenderness at the posterior edge or tip of either malleolus, and inability to bear weight both right after the injury and at the examination.

When is an ankle x-ray needed under the Ottawa rules?

This page doesn't give disposition advice. It shows how the findings combine; what to do next depends on the clinical context.

Does being unable to walk right after the injury count on its own?

No. It counts when the person also can't take four steps at the examination.

Where exactly do you press?

At the posterior edge or tip of the lateral and medial malleoli.

Do the Ottawa ankle rules apply to the foot?

The foot has a separate Ottawa rule. Magent's calculator covers the ankle alone.

Who developed the Ottawa ankle rules?

Ian Stiell and colleagues, in a 1992 paper in Annals of Emergency Medicine.