Injured a joint is a term used to describe an injury to a joint, such as a sprain. A sprain is an injury to a ligament, which is the tissue that connects two bones at a joint. Sprains can be caused by sudden or excessive stretching of the ligament, and can range from mild to severe. Symptoms of a sprain include pain, swelling, bruising, and difficulty moving the affected joint. Treatment for a sprain typically includes rest, ice, compression, and elevation.