There are three types of ligaments in the human body. The most common form of ligament is the tough, fibrous tissue that connects one bone to another bone forming a joint. The ligaments provide joint stability. Their primary function is to prevent movement that might damage a joint. Ligaments are also slightly stretchy, so they provide a limited range of motion at the joint, but they generally do not provide the same level of joint movement as muscles.
Ligaments can be found in many joints, such as the neck, shoulder, wrist, knee and spine. You can feel ligaments at work by trying to bend your elbow backwards. Ligaments prevent the elbow joint from extending backward. Ligaments provide similar range of motion control for other joints. Ligaments also stabilize joints, so that bones stay properly aligned during movement.
Since ligaments do not stretch very much, they are easily damaged by excessive stretching. For example, tearing the anterior cruciate ligament (ACL) behind the knee is a common injury in rough sports, such as football. If a ligament is injured, it can take a very long time to heal. Sometimes a damaged ligament needs surgery to repair the tear.