A sprain is a painful wrenching or tearing of the ligaments of a joint, such as an ankle or wrist. It may result from a strain, a more general term that implies misuse, overuse, or overexertion. That is, a strain is a stretching or forcing beyond proper limits: "Because he strained ligaments when he landed, he sprained his ankle."
Dictionary of problem words and expressions. Harry Shaw. 1975.