ligament, strong band of white fibrous connective tissue that joins bones to other bones or to cartilage in the joint areas. The bundles of collagenous fibers that form ligaments tend to be pliable but not elastic. They therefore permit freedom of movement within a certain limited range while holding the attached bones firmly in place. For example, the ligaments at the knee limit the movement of the lower leg to a certain range. Other types of ligaments form fibrous sheets that support such internal organs as the kidneys and the spleen.