This is the most common form of arthritis, affecting about 21 million Americans. In OA, the cartilage in the effected joint(s) breaks down, resulting in joint pain and swelling. OA typically progresses in multiple phases, beginning with a loss of cartilage elasticity. This loss of elasticity means that the cartilage is more easily damaged by injury or overuse. When the cartilage begins to break down, the bone in the affected joint thickens and bone spurs develop. Bits of bone or cartilage may be found floating in the space between the bones of the joint. At this point, the breakdown of the cartilage causes the lining of the joint to become inflamed. In reaction to the inflammation, the body produces proteins and enzymes that cause additional damage to the joint.

In OA, affected joints typically hurt the most after periods of inactivity or after periods of overuse. OA can affect the middle and end joints of the fingers, the knees, the hips, the neck, and the spine. This disease usually starts after the age of 40 and develops slowly over a period of years. With OA, joint redness and swelling are usually minimal and morning stiffness is usually sort in duration. People with OA generally do not experience a general feeling of sickness due to the disease.

Risk factors for OA include heredity, obesity, weak muscles, injury, overuse, and aging. Managing OA consists of engaging in activities and behaviors that are aimed at counteracting some of these risk factors. Physical or occupational therapy may be used, aerobic exercise along with plenty of stretching is often very helpful, as is maintaining a healthy weight. Medications typically used in the treatment of OA include pain relievers, anti-inflammatory drugs, and glucocorticoid injections. A class of medication known as hyaluronic acids may also be used to lubricate and cushion the affected joints.