There are a number of types of arthritis, with the most common being osteoarthritis, rheumatoid arthritis and juvenile arthritis. Osteoarthritis (OA) is the most common, affecting most adults at some point, and is caused by the erosion of cartilage between bone joints. Junior rheumatoid arthritis (JRA) is a common illness found in children, while rheumatoid arthritis (RA) in adults is a painful, chronic disease.
OA often causes bumps to form on the bones under the skin. The bones thicken as a result of the friction and form cysts, or spurs, that often are visible under the skin.
Joints affected by all kinds of arthritis may feel hot to the touch as the cartilage becomes inflamed.
OA causes stiffness when the joint is moved, since there is not enough good cartilage to hydrate the movement. A creaking sound also may be present when the joint is moved.
RA and JRA can cause swelling and redness in the areas of the joints when the arthritis flares up; the joints also will feel stiff and sore.
Rheumatoid arthritis can cause joints to slip out of place, creating a disfigurement that affects movement and limits regular activities.