What Is It?
Inside a joint, a tissue called cartilage cushions the joint and prevents the bones from rubbing against each other. Osteoarthritis occurs when the cartilage of a joint erodes (breaks down). Bones begin to rub against each other, causing pain and difficulty moving the joint. Osteoarthritis also can affect nearby bones, which can become enlarged in places. These enlargements are called bone spurs or osteophytes.
Although the term arthritis means joint inflammation, there is relatively little inflammation in the joints of most people with osteoarthritis. For this reason, and because this type of arthritis seems to be caused by age-related degeneration of the joints, many experts and health care professionals prefer to call it degenerative joint disease.