Sometimes it is called degenerative joint disease or osteoarthrosis.
Cartilage is the slippery tissue that covers the ends of bones in a joint.
Healthy cartilage allows bones to glide over one another. It also absorbs energy from the shock of physical movement. In osteoarthritis, the surface layer of cartilage breaks down and wears away. This allows bones under the cartilage to rub together, causing pain, swelling, and loss of motion of the joint. Over time, the joint may lose its normal shape.