polyarticular

Juvenile arthritis (JA) is arthritis that happens in children. It causes joint swelling, pain, stiffness, and loss of motion. It can affect any joint, but is more common in the knees, hands, and feet. In some cases it can affect internal organs as well.

The most common type of JA that children get is juvenile idiopathic arthritis. There are several other forms of arthritis affecting children.

One early sign of JA may be limping in the morning. Symptoms can come and go. Some children have just one or two flare-ups. Others have symptoms that never go away. JA can cause growth problems and eye inflammation in some children.

No one knows exactly what causes JA. Most types are autoimmune disorders. This means that your immune system, which normally helps your body fight infection, attacks your body's own tissues.

JA can be hard to diagnose. Your health care provider may do a physical exam, lab tests, and x-rays. A team of providers usually treats JA. Medicines and physical therapy can help maintain movement and reduce swelling and pain. They may also help prevent and treat complications.

NIH: National Institute of Arthritis and Musculoskeletal and Skin Diseases