Ligament

A ligament is a strong band of dense connective tissue, made mostly of collagen, that connects bones to each other at a joint. Where tendons anchor muscle to bone, ligaments link bone to bone. Most of their fibers lie in parallel, though not all of them do, which helps a ligament resist pulling forces from more than one direction.

Ligaments hold the bones of a joint together, guide its normal movement and stop it from bending too far or in the wrong direction. At a synovial joint, a ligament may be part of the wall of the joint capsule (intrinsic), lie outside the capsule (extrinsic) or run inside it (intracapsular), as the cruciate ligaments of the knee do. A few ligaments, such as some between the vertebrae, contain extra elastin, so they can stretch and recoil.

A ligament that is overstretched or torn produces a sprain, which ranges from a mild stretch to a complete rupture or detachment from the bone. Because ligaments have relatively few blood vessels, they heal slowly. The same word is used for folds of tissue that hold internal organs in place, such as the falciform ligament of the liver.