Arthritis, which literally means inflammation of a joint (where two or more bones meet), actually refers to more than 100 different diseases. Rheumatic diseases include any diseases that cause pain, stiffness, and swelling in joints or other supportive body structures, such as muscles, tendons, ligaments, and bones. In fact, the group of arthritis diseases falls under the category of rheumatic diseases.

Arthritis and other rheumatic diseases are often mistakenly associated with old age, because osteoarthritis (the most common form of arthritis) occurs more often among older persons. However, arthritis and other rheumatic diseases affect people of all ages. Arthritis affects nearly 300,000 children in the US.