In this use, a ligament is a short band of tough fibrous connective tissue composed mainly of long, stringy collagen fibres. Ligaments connect bones to other bones to form a joint. They do not connect muscles to bones; that is the function of tendons. Some ligaments limit the mobility of articulations, or prevent certain movements altogether.
Ligaments are only slightly elastic; when under tension, they gradually lengthen. This is one reason why dislocated joints must be set as quickly as possible: if the ligaments lengthen too much, then the joint will be weakened. Athletes, gymnasts, dancers, and martial artists perform stretching exercises to lengthen their ligaments, making their joints more supple. The consequence of a broken ligament can be instability of the joint. Not all broken ligaments need surgery, but if surgery is needed to stabilise the joint, the broken ligament can be joined.