Osteoarthritis is a form of arthritis that features the breakdown and eventual loss of the cartilage of one or more joints. Cartilage is a protein substance that serves as a “cushion” between the bones of the joints. Among the over 100 different types of arthritis conditions, osteoarthritis is the most common. Osteoarthritis occurs more frequently as we age. Before age 45, osteoarthritis occurs more frequently in males. After 55 years of age, it occurs more frequently in females. In the United States, all races appear equally affected. Osteoarthritis is abbreviated as OA or referred to as degenerative arthritis or degenerative joint disease (DJD). Osteoarthritis commonly affects the hands, feet, spine, and large weight-bearing joints, such as the hips and knees.
Primary osteoarthritis, osteoarthritis not resulting from injury or disease, is mostly a result of natural aging of the joint. With aging, the water content of the cartilage increases, and the protein makeup of cartilage degenerates. Eventually, cartilage begins to degenerate by flaking or forming tiny crevasses. In advanced osteoarthritis, there is a total loss of the cartilage cushion between the bones of the joints. Repetitive use of the worn joints over the years can irritate and inflame the cartilage, causing joint pain and swelling. Loss of the cartilage cushion causes friction between the bones, leading to pain and limitation of joint mobility. Inflammation of the cartilage can also stimulate new bone outgrowths (spurs, also referred to as osteophytes) to form around the joints. Osteoarthritis occasionally can develop in multiple members of the same family, implying a hereditary (genetic) basis for this condition.