A sprain is an injury to the ligaments, which help to hold the bones together. A sprain is different from a strain, which is an injury to a tendon. The most common sprains happen to the ankle or the wrist, although they sometimes occur in the shoulder, elbow, neck or back. Sprains occur when a joint is forced past its normal limit or range. Unlike muscles, ligaments are limited in blood supply and, as a result, take a relatively long time (4-16 weeks) to heal.

Sprain severity is graded from a one to a three. A grade one means that the ligament is slightly stretched and only some of the fibers are torn. A grade two means that more of the fibers are torn or that several, but not all of the ligaments are torn. A grade three usually indicates that all of the ligaments have been fully or completely torn.

A sprain initially results in swelling. Immobilization and/or support helps in the first stages of healing. The ligament gradually repairs itself and gains strength, and the joints regain support. The scar tissue usually is not as strong as the original ligament and the joint may retain some instability.

Physical therapy can help in the rehabilitation of sprains in several ways. Modalities such as ultrasound, heat, cold and electrical stimulation can aid in healing and control of pain. In the later stages of healing, therapeutic exercise can help the ligaments regain strength and endurance, as well as motion in the joint. Functional braces may be issued to prevent re-injury during activity.