About 30% of all children with juvenile rheumatoid arthritis (JRA) have polyarticular disease, in which five or more joints are affected. The disease usually affects small joints, such as those in the hands and feet, but the disease may also affect large joints. Polyarticular JRA often affects the same joints on both sides of the body. Some children have a more severe form of the disease, which doctors think is similar to adult rheumatoid arthritis.