Your ligaments are tough, elastic-like bands that connect bone to bone and hold your joints in a place. A sprain is an injury to a ligament caused by tearing of the fibers of the ligament. The ligament can have a partial tear, or it can be completely torn apart.
Ankle sprains are the most common type of sprain. Wrist, knee and thumb sprains are also common. Sprained ligaments often swell rapidly and are painful. Generally, the greater the pain and swelling, the more severe the injury is. For most minor sprains, you probably can start initial injury treatment yourself.