Best X-Ray Views for Acute Ankle Injury
For acute ankle injuries meeting Ottawa Ankle Rules criteria, order three standard views: anteroposterior (AP), lateral, and mortise views that include the base of the fifth metatarsal distal to the tuberosity. 1
Standard Three-View Protocol
The American College of Radiology establishes this three-view series as the appropriate initial imaging for patients with positive Ottawa Ankle Rules, which include: 1
- Inability to bear weight immediately after injury
- Point tenderness over the medial malleolus, posterior edge or inferior tip of the lateral malleolus, talus, or calcaneus
- Inability to ambulate 4 steps in the emergency department
This protocol achieves 92-99% sensitivity for detecting ankle fractures. 1
Critical Technical Considerations
Field of View Requirements
The imaging must extend to include the base of the fifth metatarsal distal to the tuberosity to avoid missing associated fractures. 1 This is essential because in patients with inversion injuries or ankle fractures, isolated foot fractures beyond the fifth metatarsal base are rare and do not warrant separate foot radiographs. 1
Weight-Bearing Views When Possible
If the patient can tolerate it, obtain weight-bearing radiographs to assess fracture stability, particularly for malleolar fractures where stability determines treatment. 1 A medial clear space <4 mm on weight-bearing films confirms stability. 1
Common Pitfalls and Special Scenarios
Do Not Routinely Add Foot or Knee Views
Avoid ordering concurrent foot or knee radiographs in the presence of ankle inversion injury or fracture due to extremely low yield. 1 This represents unnecessary radiation exposure and cost without diagnostic benefit. 1
When Two Views May Be Considered
While some older research suggests lateral and mortise views alone may be sufficient for fracture diagnosis 2, 3, the ACR guideline standard remains three views 1, and more recent pediatric data shows statistically significant decreased accuracy and sensitivity with only two views. 4 The three-view protocol should be followed to avoid missing fractures.
Additional Views for Specific Clinical Scenarios
Consider supplemental views only when specific injuries are suspected: 1
- Axial Harris-Beath view: For suspected calcaneal fractures to determine intra-articular extent 1
- Broden view: For lateral talar process fractures (snowboarder's fracture), which are missed on routine radiographs 40-50% of the time 1
- Gravity stress views: More reliable than manual stress views for evaluating supination-external rotation injuries with suspected deltoid ligament disruption 1, 5
- Anterior talofibular ligament view: May identify occult distal fibular avulsion fractures in children with lateral ankle sprains, detecting fractures in 26% of cases missed on standard views 1
When NOT to Order Radiographs
If Ottawa Ankle Rules are negative (no point tenderness over malleoli/talus/calcaneus, able to walk), do not order any imaging. 1 This clinical decision rule safely excludes fractures without radiation exposure.
Advanced Imaging Is Not First-Line
Do not order CT, MRI, bone scan, or ultrasound as initial imaging for acute ankle trauma with positive Ottawa Ankle Rules. 1 These modalities are reserved for: 1
- CT: Polytrauma patients or complex fracture characterization for surgical planning
- MRI: Occult fractures after negative radiographs with persistent symptoms, or suspected ligamentous injuries
- Neither bone scan nor ultrasound are appropriate first-line studies 1
Pre-Imaging Precaution
Avoid manipulating the ankle before obtaining radiographs unless there is neurovascular compromise or critical skin injury, as this may necessitate re-manipulation or cause complications. 1