A sprain is an injury in a joint, caused by the ligament being stretched beyond its own capacity. A muscular tear caused in the same manner is referred to as a strain. In cases where either ligament or muscle tissue is torn, immobilization and surgical repair may be necessary. Ligaments are tough, fibrous tissues that connect bones to other bones. Sprains can occur in any joint but are most common in the ankle and wrist.
The diagnosis of a sprain injury is made by a physical examination. In most cases an x-ray (or stress x-ray) of the affected joint is obtained to ensure that there are no fractures. If a tear in the ligament is suspected, then an MRI or arthroscopy is obtained. MRI is usually ordered after swelling has subsided and can readily identify the presence of a ligament injury.
Sprains typically occur when the joint is overextended. This can cause over stretching of the joints, tear or slipping of the ligament.