Six steps in the ED sounds reassuring. But an Ottawa Ankle Rules question may be testing something narrower: what the walking finding means, and whether the rule covers the area that hurts. The useful board-prep skill is a scope audit—check the target region, each criterion, and what remains outside the rule before calling the result negative.
Start with the rule’s target, not the step count
The Ottawa Ankle Rules (OAR) guide radiography decisions after acute blunt ankle and foot injury. They address fractures in defined malleolar and midfoot regions; they are not a general screen for every fracture in the foot. The ankle and foot criteria are separate:
| Radiograph series | Pain zone required | OAR finding that indicates radiography |
|---|---|---|
| Ankle | Malleolar zone | Bone tenderness at the posterior edge of the distal 6 cm or tip of either malleolus, or inability to take four steps both immediately after injury and during evaluation |
| Foot | Midfoot zone | Bone tenderness at the navicular or base of the fifth metatarsal, or inability to take four steps both immediately after injury and during evaluation |
When pain is in one of those zones, the rule is negative for its target region only if there is no listed landmark tenderness and the patient can take at least four steps at both time points. The rule is intended for eligible patients with an assessable acute injury; if exclusionary circumstances prevent applying it, call it unevaluable rather than negative. If the stem does not establish the required pain zone or leaves a criterion unclear, do not silently fill in the missing fact.
Apply the case without adding facts
The vignette reports that the patient can take six steps in the ED. That establishes her ability to walk at the time of evaluation; it does not tell us whether she could take four steps immediately after the injury. A board-ready statement is conditional: if she could take at least four steps at both times, the OAR inability-to-bear-weight criterion is absent. That fact alone does not rule out fracture.
Walking does not cancel tenderness at an OAR landmark. For example, if a patient has midfoot pain and navicular tenderness, the foot-radiograph criterion is met even if the patient walks into the department.
The case also gives tenderness over the calcaneus and third metatarsal head. Neither is among the four classic OAR tenderness landmarks. Keep that statement separate from the imaging decision: the ACR acute ankle imaging criteria treat focal calcaneal or talar tenderness as a reason for ankle radiography, while ACR foot criteria support radiography when suspected pathology lies in an area not addressed by OAR, such as a metatarsal. So calcaneal tenderness is not a classic OAR-positive landmark, but it should not be used to call the ankle assessment reassuring; assess the possible metatarsal injury separately as well.
That distinction matters in multiple-choice questions. If asked what the weight-bearing criterion means, answer that branch precisely. If asked whether imaging can be omitted for the whole patient, assess the pain zone, every rule criterion, and any concerning finding outside the rule’s scope.
Four reasoning errors that make a negative rule look stronger than it is
- Reversing the threshold: The trigger is inability to take four steps at both time points—not simply the presence or absence of a limp now.
- Collapsing two time points into one: Current walking does not supply the missing history of immediate post-injury function.
- Letting function override tenderness: A negative weight-bearing branch does not erase positive tenderness at a specified landmark.
- Extending the rule beyond its target: High sensitivity in the regions studied is not a universal guarantee against fractures elsewhere in the foot.
The most important correction is to keep the rule’s output narrow. A negative OAR result speaks to the target region and the criteria assessed; it does not replace clinical assessment of a different focal injury or other applicable imaging guidance.
A five-minute revision exercise: change one fact at a time
Close your notes. Draw two rows—ankle and foot—and retrieve, from memory, the required pain zone, the tenderness landmarks, and the four-step condition. Then return to the vignette and mark each fact as known, missing, or outside the rule’s landmarks. Only after making that attempt, check your reference.
Now change one detail at a time and state what changes:
- Add navicular tenderness with midfoot pain; keep the patient able to walk. The foot-radiograph criterion is met. Walking does not cancel landmark tenderness.
- Keep tenderness at the third metatarsal head; document that she walked at both time points. The OAR weight-bearing criterion is absent, but the rule does not assess that tender site. If injury there remains a concern, consider imaging under the applicable foot-trauma guidance.
- Keep the six steps in the ED; leave immediate post-injury ability undocumented. You cannot conclude that the two-time-point weight-bearing condition has been established from the vignette alone.
For each version, write one sentence naming the rule’s result and a second sentence naming what still needs clinical judgment. This is retrieval practice because you reconstruct the criteria before looking them up; changing one fact at a time helps expose exactly which branch of your reasoning moved.
Practical takeaways
- First confirm that the patient’s injury and pain location fit the rule’s target and that the rule can be validly assessed.
- Four steps at both time points address only the weight-bearing criterion; they do not overrule tenderness at a listed landmark.
- Calcaneal tenderness is not one of the classic four OAR landmarks, but ACR acute ankle criteria treat focal calcaneal tenderness as a reason for ankle radiography. Suspected injury at an off-rule metatarsal site may also warrant foot radiography under ACR criteria.
