The term ‘arthritis’ refers to inflammation of one or more joints. Because of inflammation, arthritis is often accompanied by pain in the extremities. Osteoarthritis (OA) is the most common joint disorder, and it develops from wear and tear on a joint, like from aging. Most people with OA are older, but young people can also develop this kind of arthritis after injury or repetitive stress. Rheumatoid arthritis (RA), another common kind of arthritis, is an autoimmune disorder, which means the body’s immune system abnormally attacks healthy tissue. RA leads to inflammation in joints, surrounding tissues and even other organs.