Fracture / Osteochondral Lesion / Infection — the ankle safety screen

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Three branches, and they do not share a timeline:

The one thing to take from this page:

A negative Ottawa rule and a negative X-ray both clear a fracture — and nothing else.

You'll often be taught this as a day-one screen. Two of the three branches aren't.

Fracture is a day-one decision, and the Ottawa Ankle Rules are built for exactly that. The osteochondral lesion is not — it hides inside a sprain that isn't settling, and cartilage and osteochondral lesions are not rare after acute ligamentous ankle injury [1]. Infection has no timeline at all.

⚠️ No national Australian guideline governs this decision; NSW's emergency care protocol (Agency for Clinical Innovation) uses the Ottawa Ankle Rules for it. The Ottawa Ankle Rules are a decision rule about whether to X-ray, anchored to Bachmann et al. 2003 [2] and Gomes et al. 2022 [3]. Imaging referral rights differ by state and setting — check what you are permitted to request where you are working.

Five stages — and on an acute traumatic presentation your course reorders them: MAIN PROBLEM → BODY CHART → HISTORY → BEHAVIOUR. That order is used here.

MAIN PROBLEM

"I rolled it and I heard something."
"It came up like a balloon within about twenty minutes."
"I couldn't put any weight on it at all."

And, six weeks later:
"It's still not right. There's a deep ache and it catches."

BODY CHART

• Mark the malleoli, the base of the fifth metatarsal and the navicular specifically. These are the sites the rule cares about.
• Mark swelling and bruising distribution — and note how fast it came up.
• If this is a review appointment, mark where the pain is now versus where it was. A pain that has migrated deep and central after a lateral sprain is the OLT question.

HISTORY

• Mechanism: twist, inversion, or a direct blow. Get the foot position if they can give it.
• Audible crack or pop.
• Speed of swelling. Rapid swelling and bruising within the hour is a different story from a swelling that built over a day.
• Could they weight-bear immediately, and can they take four steps now?
• Any open wound, previous surgery, or metalwork in that ankle? Fracture-related infection follows wounds, surgery, hardware and delayed healing (Krez et al. 2025).
• Diabetes, neuropathy, immunosuppression — the infection risk set.

BEHAVIOUR

• Aggs / Eases as usual — and for the OLT branch, ask specifically about deep aching after activity, catching, giving way, and swelling that keeps returning.
• Night and rest pain, fever, malaise → the infective branch.

SPECIAL / SCREENING QUESTIONS

• Fever, chills, feeling unwell — at any point in the episode, not just today.
• Is it getting better, staying the same, or getting worse? Getting worse after an acute ankle injury is not a normal trajectory.

What the ranking is really doing here

On day one it is a fracture question. Apply the rule, image if it is positive, and do not label it a sprain until bony injury is excluded.

At six weeks it is a completely different question, and the ranking flips: a sprain that isn't settling makes the OLT the leading hypothesis, not the outlier. In children and adolescents this needs extra care — open physes change both the injury and the imaging (Anastasio et al. 2023), and the Ottawa rules can be applied in younger patients but with developmental and communication limits in mind (Carvalho et al. 2025).