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Ankle XRay

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Ankle XRay, Ottawa Ankle Rule, Low Risk Ankle Rule

  • See Also
  1. Ankle Anatomy
  2. Ankle Exam
  3. Foot XRay
  • Indications
  • Ottawa Ankle Rules in Acute Ankle Sprain (Over age 5 years old)
  1. Ankle XRay not needed if both are true:
    1. Able to ambulate at injury or in ER for 4 steps
    2. No pain over distal posterior 6 cm (2.4 inches) of tibia, fibula
  2. Foot XRay not needed for mid-Foot Pain if both true:
    1. Able to ambulate at injury or in ER for 4 steps
    2. No pain at fifth Metatarsal base and Tarsal Navicular
  3. Efficacy
    1. Test Sensitivity for Malleolar Fracture: 95%
    2. Requires alert adult or child age 5 or older
    3. Injury within prior 10 days
  • Indications
  • Low Risk Ankle Rule (children over age 3 years old)
  1. Ankle XRay is not needed if:
    1. No marked swelling, deformity or malalignment AND
    2. No pathologic Fracture risk AND
    3. Tenderness is limited to distal fibula (distal to anterior tibial joint line) and lateral ligaments
  2. Efficacy
    1. Children must be over age 3 years old
    2. Finds high risk injury (e.g. distal tibia, proximal fibula, Ankle Dislocation) in 98-100% of those age >3 years old
    3. Misses nondisplaced distal fibula avulsion Fractures and Salter-Harris I and II Fractures
  3. References
    1. Boutis (2013) CMAJ 185(15):E731-8 +PMID:23939215 [PubMed]
    2. Ramasubbu (2015) Pediatr Emerg Care 31(10):685-7 +PMID:26196362 [PubMed]
  • Technique
  • Views
  1. Anteroposterior Ankle
    1. Lateral Malleolus
    2. Medial Malleolus
    3. Talar Dome (talus)
    4. Tibial Plafond (distal tibia that articulates with the talar dome)
    5. Distal Tibiofibular joint (syndesmosis)
  2. Lateral Ankle
    1. Posterior Malleolus
    2. Talar Dome
  3. Oblique Ankle (Ankle Mortise View)
    1. Modified anteroposterior view perpendicular to the ankle mortise
    2. Leg internally rotated 15 to 20 degrees
  • Imaging
  • Pitfalls
  1. Growth Plate Fracture in adolescent
    1. May be missed on Ankle XRay
    2. Consider if pain over lateral malleolus (fibula)
  2. Ankle Syndesmotic Sprain (High Ankle Sprain)
    1. Tibiofibular clear space widening >6 mm
  3. Ankle mortise
    1. Space around the talus should be consistent (symmetric) at its margin between the tibia and fibula
  4. Os Trigonum is a normal variant (lateral xray)
    1. Os Trigonum is an Ossification Center posterior to the talus
    2. Normal variant seen on lateral Ankle XRay in up to 14% of patients
  5. Ankle Fracture Stability (Weber A, B and C)
    1. ankleFractureWeberABC.jpg
    2. See Ankle Fracture
  • Evaluation
  1. See Musculoskeletal XRay ABCs (systematic XRay approach)
  2. Alignment and Adequacy
    1. Distal tibia and fibula should be visible
    2. Base of the fifth Metatarsal should be visible
  3. Bones
    1. Start distally, at bottom of film (work proximally up the film)
    2. Trace each bony cortex
      1. Distinguish true Fracture lines (that stop at cortex) from Mach Bands (overlapping shadows)
    3. Review foot bones visible in film
      1. See Foot XRay
      2. Calcaneus and Talus
      3. Fifth Metatarsal base
    4. Review distal tibia and fibula
      1. Posterior malleolus
  4. Cartilage (Joint spaces)
    1. Ankle mortise with consistent spacing around the talar dome
    2. Distal tibial-fibular joint should overlap on mortise view
  5. Soft Tissue
    1. Ankle effusion (best seen on lateral ankle view)
      1. Fluid or hemarthrosis will appear more radiopaque (brighter white)
      2. Replaces the typical radiolucent (darker) fat the surrounds the joint (seen immediately adjacent to the joint line)
  • References
  1. Tubbs and Janicki (2025) Adult Lower Extremity: Ankle, Mastering Emergency Imaging, CCME, accessed 5/10/2026
  2. Labovitz (1998) Foot Ankle Int 19:661-7 [PubMed]
  3. Stiel (1994) JAMA 271:827-32 [PubMed]