Arthritis means "joint inflammation" and refers to a group of diseases that cause pain, swelling, stiffness, and loss of motion in the joints. "Arthritis" is often used as a more general term to refer to the more than 100 rheumatic diseases that may affect the joints but can also cause pain, swelling, and stiffness in other supporting structures of the body such as muscles, tendons, ligaments, and bones. Some rheumatic diseases can affect other parts of the body, including various internal organs. Children can develop almost all types of arthritis that affect adults, but the most common type that affects children is juvenile rheumatoid arthritis.