Acute lateral ankle ligament sprain

Lateral ankle ligament sprain is the most common type of sprain and is a clinical diagnosis. Investigation is rarely required except in cases of suspected grade 3 injury (complete tear) or to rule out a potential fracture or ankle syndesmosis injury. If there is suspicion of an associated fracture, the Ottawa ankle rules can aid clinicians in deciding whether an X-ray is required; see Ottawa ankle rules for this clinical decision toolStiell, 1992. Ultrasound can demonstrate injuries to superficial ligaments, but diagnosis can most often be made on clinical examination.

Figure 1. Ottawa ankle rules

An ankle X-ray series is only required if there is:

  • pain near the malleoli AND
  • 1 or more of
    • age 55 years or more
    • unable to weightbear for 4 steps both immediately and when examined by doctor
    • bony tenderness at the posterior edge (up to 6 cm) or posterior tip of either malleolus.

Note: Adapted from Stiell IG, Greenberg GH, McKnight RD, Nair RC, McDowell I, Worthington JR. A study to develop clinical decision rules for the use of radiography in acute ankle injuries. Ann Emerg Med 1992;21(4):384-90 with permission from Elsevier. https://www.ncbi.nlm.nih.gov/pubmed/1554175