Arthritis is inflammation of one or more joints and it involves the breakdown of cartilage. Cartilage normally protects a joint, allowing it to move smoothly. Cartilage also absorbs shock when pressure is placed on the joint, such as when you walk. Without the normal amount of cartilage, the bones rub together, causing pain, swelling (inflammation), and stiffness. Usually the joint inflammation goes away after the cause goes away or is treated. Sometimes it does not. When this happens, you have chronic arthritis. Arthritis may occur in men or women. Osteoarthritis is the most common type.
Source: NIH.gov
