Arthritis is an inflammation of the joints. It can affect one joint or multiple joints. There are more than 100 different types of arthritis, with different causes and treatment methods. Two of the most common types are osteoarthritis (OA) and rheumatoid arthritis (RA).
The symptoms of arthritis usually develop over time, but they may also appear suddenly. Arthritis is most commonly seen in adults over the age of 65, but it can also develop in children, teens, and younger adults. Arthritis is more common in women than men and in people who are overweight.
Joint pain, stiffness, and swelling are the most common symptoms of arthritis. Your range of motion may also decrease, and you may experience redness of the skin around the joint. Many people with arthritis notice their symptoms are worse in the morning.
In the case of RA, you may feel tired or experience a loss of appetite due to the inflammation the immune system’s activity causes. You may also become anemic — meaning your red blood cell count decreases — or have a slight fever. Severe RA can cause joint deformity if left untreated.
Cartilage is a firm but flexible connective tissue in your joints. It protects the joints by absorbing the pressure and shock created when you move and put stress on them. A reduction in the normal amount of this cartilage tissue causes some forms of arthritis.
Normal wear and tear cause OA, one of the most common forms of arthritis. An infection or injury to the joints can exacerbate this natural breakdown of cartilage tissue. Your risk of developing OA may be higher if you have a family history of the disease.
Another common form of arthritis, RA, is an autoimmune disorder. It occurs when your body’s immune system attacks the tissues of the body. These attacks affect the synovium, a soft tissue in your joints that produces a fluid that nourishes the cartilage and lubricates the joints.