The articulating portions of a ball and socket joint are cushioned by a firm, smooth tissue called articular cartilage. Healthy articular cartilage minimizes friction between joints and prevents damage to the bones as they glide smoothly against one another. When articular cartilage is damaged, due to osteoarthritis or other conditions, small pieces of cartilage may break loose into the synovial fluid. Similarly, after a fracture, small fragments of bone, or bone attached to cartilage, may float into the joint space. These small fragments of cartilage or bone inside the joint that are not normally present are collectively known as loose bodies.