Lateral ankle sprain — RACGP Fellowship MCQ

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EasyMusculoskeletal and sportsLateral ankle sprainRACGP Fellowship

A 28-year-old footballer twists his ankle and can walk four steps in your clinic. There is tenderness over the anterior talofibular ligament but not the posterior malleoli, navicular or base of fifth metatarsal. What is the most appropriate investigation?

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Correct answer: D — No ankle radiograph is required

This patient has a classic isolated lateral ankle sprain (anterior talofibular ligament tenderness with normal functional capacity). The Ottawa Ankle Rules state that ankle radiography is indicated only if the patient is unable to walk four steps after injury or if there is bone tenderness along the posterior distal 6 cm of the fibula/tibia or over the malleoli. This patient meets neither criterion: he walks four steps and has no malleolar or midfoot tenderness. Plain radiography is unnecessary and exposes the patient to avoidable radiation. CT and bone scan are second-line tools for suspected occult fractures (not indicated here) or persistent symptoms after failed conservative management. MRI is not required for uncomplicated ligamentous injuries in primary or emergency settings. Correct application of the Ottawa Ankle Rules reduces unnecessary imaging while maintaining high sensitivity for clinically significant fractures.

Reference: Ottawa Ankle Rules. Endorsed by Royal College of Radiologists; applied in Australian emergency medicine and RACGP practice. See: Traumatic Ankle Injuries in the Emergency Department (PMC 2024); Clinical Value of the Ottawa Ankle Rules (PLoS ONE 2013); RACGP Sports ankle injuries: Assessment and management (2010). https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12661380/