ligament

A ligament is the band of connective tissue that holds two bones together at a joint. It is the joint's keeper: it lets the joint move in the directions its surfaces allow and resists movement in the directions that would take the bones apart. Ligaments sit beside tendons in every anatomy diagram, and the pair is a favorite exam question because one word changes the whole answer — a tendon ties a muscle to a bone, and a ligament ties a bone to a bone. The joint's movement itself does not come from the ligament: it comes from the shape of the surfaces where the bones meet, which is why the shoulder moves in every direction and the elbow works like a door. Ligaments limit a joint and hold it together, and they do no pulling of their own.