Ligaments help to form, align and control joints in the body as they are the minimally elastic connective tissues that hold one bone to the other. Ligaments are composed of tough fibrous but dense strands of collagen. They are often confused with tendons which connect muscles to bones.
To hold the joint in place, ligaments are arranged in a criss-cross manner between the bones to ensure that the joint does not become loose. Though they may stretch very slightly, the ligaments exist to control the range of movement in a joint. Muscles can be trained to lengthen and become more flexible, but the ligament remains the same as its role is to simply support the joint. This why joints such as the knees and elbows only bend in one direction. This limit in direction is a sign that the ligament has reached its maximum lengthening tension.
Overly stretching a ligament can cause injury and cause a joint to become less flexible. Once a ligament is stretched over its limit, it cannot retain its proper shape. Surgery and physical therapy is available for ligament injuries, but the flexibility rarely returns, instead repeat injury increases. There is very little blood supply that travels through the joints and ligaments meaning that they do not heal well or only do so after a long time. This explains why dislocations in the joints are recurrent; they may be repaired but the joint would have already weakened and any pressure dislocates it again as the elongated ligaments cannot adequately support the joint.