Arthritis is a joint disorder featuring inflammation. A joint is an area of the body where two different bones meet. A joint functions to move the body parts connected by its bones. Arthritis literally means inflammation of one or more joints. Arthritis is frequently accompanied byjoint pain. Joint pain is referred to asarthralgia. There are many types of arthritis (over 100 identified, and the number is growing). The types range from those related to wear and tear of cartilage (such as osteoarthritis) to those associated with inflammation resulting from an overactive immune system (such as rheumatoid arthritis). Arthritis is classified as one of the rheumatic diseases. They are similar in that they have a tendency to affect the joints, muscles, ligaments, cartilage, and tendons, and many have the potential to affect other internal body areas.