What Is It?
A sprain is a tear of ligaments, the tough bands of fibrous tissue that connect bones to one another at a joint. Normally, ligaments stabilize a joint, keep the joint's bones aligned and limit the motion of a joint to the normal range. When a joint is sprained, its torn or stretched ligaments can lose part or all of their ability to reinforce the joint and to keep it moving normally. In severe cases, the sprained joint can become unstable and loose, bones can move out of alignment and the joint may extend beyond its normal range of motion.
Although ligaments can be sprained in a variety of ways, the actual ligament damage is usually caused by at least one of the following: