When is an X-ray (X-ray) recommended for an ankle sprain to rule out a fracture or dislocation?

When to Order X-rays for Ankle Sprains

Use the Ottawa Ankle Rules (OAR) to determine if radiographs are needed—X-rays are indicated only when the patient cannot bear weight immediately after injury, cannot take 4 steps in the emergency department, or has point tenderness over specific bony landmarks (medial malleolus, posterior edge or inferior tip of lateral malleolus, talus, or calcaneus). 1

Clinical Decision Algorithm

Step 1: Apply Ottawa Ankle Rules (OAR)

Order ankle X-rays if ANY of the following criteria are met: 1

• Inability to bear weight immediately after the injury
• Inability to ambulate 4 steps in the emergency department
• Point tenderness over:
  • Medial malleolus
  • Posterior edge or inferior tip of the lateral malleolus
  • Talus
  • Calcaneus

Do NOT order X-rays if: 1

• Patient can walk
• No point tenderness over the specified bony landmarks
• No exclusionary criteria present (neurologically intact, no peripheral neuropathy)

The OAR have excellent sensitivity (92-100%) for detecting fractures, meaning they reliably rule out fractures when negative. 1, 2 The specificity is lower (16-51%), which means some patients without fractures will still get X-rays, but this is acceptable to avoid missing fractures. 2

Step 2: Consider Exclusionary Criteria

Always obtain radiographs regardless of OAR if the patient has: 1

• Peripheral neuropathy (including diabetic neuropathy)
• Neurologic disorder affecting lower extremity sensation
• Inability to cooperate with examination
• Intoxication preventing reliable assessment

These patients may have fractures without typical pain or tenderness due to impaired pain proprioception. 1

Step 3: Special Clinical Scenarios Requiring Heightened Suspicion

Consider X-rays even with borderline OAR findings in: 1

• Snowboarder's fracture (lateral talar process): Look for swelling inferior to the lateral malleolus—these fractures are missed 40-50% of the time on routine radiographs 1
• High-energy trauma or polytrauma patients 1
• Medial tenderness, bruising, or swelling suggesting increased fracture risk 1

Imaging Technique When X-rays Are Indicated

Standard three-view ankle series: 3

• Anteroposterior view
• Lateral view
• Mortise view

Weight-bearing radiographs are preferred when possible, as they provide critical information about fracture stability, particularly for malleolar fractures. 1 A medial clear space <4 mm on weight-bearing films confirms stability. 1

Common Pitfalls to Avoid

Do not routinely order foot or knee radiographs with ankle inversion injuries—the yield is extremely low. 1

Do not manipulate deformed ankles before X-rays unless there is neurovascular compromise or critical skin compromise. Manipulation before imaging significantly increases the risk of requiring re-manipulation (44% vs 18%). 4

Do not order advanced imaging (CT, MRI) acutely unless initial radiographs show a fracture requiring further characterization or if pain persists beyond 1-3 weeks with negative initial films. 1, 2

When Initial X-rays Are Negative But Symptoms Persist

If pain persists 1-3 weeks after negative radiographs: 1

• MRI without contrast is the most sensitive for occult fractures and bone marrow edema 3
• CT without contrast is excellent for detecting subtle cortical fractures 3
• These are equivalent alternatives—order only one based on availability and clinical suspicion 1

The British Journal of Sports Medicine notes that physical examination sensitivity and specificity are optimized when delayed 4-5 days post-injury, so consider re-examination before advanced imaging. 3