Juvenile arthritis, also known as juvenile chronic arthritis, childhood arthritis and juvenile idiopathic arthritis, has five different subtypes, or classifications, depending on the symptoms found within the first six months of diagnosis. These classifications are pauciarticular, polyarticular, systemic onset, spondyloarthropathy and psoriatic juvenile arthritis. Juvenile arthritis was once referred to as juvenile rheumatoid arthritis but the 'rheumatoid' was dropped as part of the name because it leads people to believe this disease is similar to rheumatoid arthritis in adults, which it is very different from in terms of symptoms, course of the disease and future outlook of the disease.

Pauciarticular juvenile arthritis affects less than four joints, usually the ankle, knee, elbow, or wrist and is the most common type of juvenile arthritis. This particular subtype affects around 45% of children diagnosed with juvenile arthritis, very few of which develop general, or body-wide, symptoms. Pauciarticular juvenile arthritis sufferers rarely experience bone growth problems or deformed joints, which may be associated with other types of juvenile arthritis. Some children with juvenile arthritis develop inflammation of the eye, known as uveitis, which can lead to blindness if it isn't treated promptly. Pauciarticular juvenile arthritis will sometimes disappear within a few years, but many children will experience cycles of remission and flares for the rest of their life.

Polyarticular juvenile arthritis affects about 40% of children diagnosed with juvenile arthritis and it affects more girls than boys. This subtype of juvenile arthritis affects children with a huge age gap and it is rarely first diagnosed between age three and ten. Polyarticular juvenile arthritis affects at least five joints at the same time, usually the small joints of the hands and feet, although the knee has been known to be affected as well. When the knee is affected by juvenile arthritis, the bones in the leg will begin to grow at different rates and one leg will become longer than the other. This can lead to arthritis in the hip or spine, which around half of all children diagnosed with this subtype of juvenile arthritis will develop. Polyarticular juvenile arthritis presents with general symptoms, such as decreased appetite, slight fever and a slight rash. Polyarticular juvenile arthritis is usually most severe in children who were primarily diagnosed after age 10 and they may test positive for rheumatoid factor. This is a marker found in other autoimmune disorders, including adult rheumatoid arthritis. If a child does test positive for this marker, they are more likely to develop deformed joints and many doctors consider this subtype of juvenile arthritis adult rheumatoid arthritis that occurs at an early age.

Systemic onset juvenile arthritis is sometimes called Still disease after the doctor who first described it. This subtype of juvenile arthritis occurs in approximately 10% of juvenile arthritis patients and affects boys and girls equally. Primary diagnosis is usually made between 5 and 10 years of age and may be difficult to diagnose accurately because the initial symptoms do not affect the joints. The initial symptoms are usually found with some type of infection, high fever, swollen lymph nodes, rash, loss of appetite and subsequent weight loss. Occasionally children with this subtype of juvenile arthritis will develop more serious complications, inflammation of the sac surrounding the heart (pericarditis), inflammation of the heart itself (myocarditis) and inflammation of the tissue lining the chest cavity and lungs (pleuritis). However, systemic onset juvenile arthritis rarely includes inflammation of the eye as seen in pauciarticular juvenile arthritis. When arthritis symptoms do begin to appear, often later in the course of this disease, they usually affect the wrists or ankles. Many of the children diagnosed with systemic onset juvenile arthritis will experience cycles of remissions and flares of the systemic symptoms throughout their childhood. Systemic onset juvenile arthritis sufferers will go on to develop polyarticular juvenile arthritis.

The final two subtypes of juvenile arthritis, spondyloarthropathy and psoriatic juvenile arthritis are rare. Spondyloarthropathy usually affects boys over the age of eight. It begins in the knees and ankles, slowly moving to include the lower spine and hips. Sometimes uveitis occurs, but resolves on its own. Psoriatic juvenile arthritis affects less than four joints in the beginning, but soon advances to other joints. The toes, hips, spine and fingers are the main joints affected by this subtype of juvenile arthritis. Children with this subtype of juvenile arthritis often suffer from psoriasis and have pits or ridges on their fingernails. This arthritis often disables the child.