The uncommon sprain. Ligamentous diastasis of the ankle without fracture or bony deformity.

A 19-year-old male patient presented with ligamentous diastasis of the ankle without fracture or bony deformity--an uncommon sprain that may be mistaken for the common ankle sprain. The author identifies four types of ligamentous diastasis of the ankle and discusses how they may be differentiated from the common ankle sprain, thus avoiding undertreatment and the initiation of premature joint degeneration.