A patient sustains a severe eversion injury of the ankle. Radiographs show an avulsion fracture of the tip of the medial malleolus. Which structure, described as the strongest of the four collateral ligaments of the ankle, has been torn?
- A Anterior talofibular ligament
- B Calcaneofibular ligament
- C Deltoid (medial) ligament ✓
- D Posterior talofibular ligament
Correct answer: C. Deltoid (medial) ligament
Explanation
The deltoid ligament is a strong triangular fan on the medial side of the ankle, attaching the medial malleolus to the talus, calcaneus, and navicular. Forced eversion strains it and may avulse the medial malleolus rather than tear the ligament itself. The three lateral ligaments listed are weaker and are injured by inversion sprains, the far more common mechanism at this joint.
Reference: Gray's Anatomy for Students, 4th ed.
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