A sprain (from the French espraindre - to wring) is an injury which occurs to ligaments caused by a sudden overstretching. The ligament is only usually stretched, but sometimes it can be snapped, slightly torn or ruptured, which are more serious and require longer to heal.

Sprains are graded in three degrees. Although some signs and symptoms can be used to assess the severity of a sprain, the most definitive method is with the use of magnetic resonance imaging. A 1° sprain has only minor tearing of the ligament whereas a 3° sprain is characterized by complete rupture.

The typical signs and symptoms associated with a sprain are localized pain, swelling, and loss of function.

Although any joint can experience a sprain, some of the more common include the ankle, knee, and thumb. Perhaps one of the more talked about sprains is that to the Anterior Cruciate Ligament of the knee. This is a disabling sprain common to athletics, especially female basketball players.

See also: strain , muscle, first aid.