Juvenile Rheumatoid Arthritis (JRA) is a form of rheumatoid arthritis with onset before 16 years of age. JRA differs from the adult form of rheumatoid arthritis is many respects. First, 70% of patients are seronegative. Second, large joints are more commonly involved as opposed to the adult disease in which small joint involvement predominates. The most commonly involved joints in JRA are: knee (epiphyseal overgrowth with widening of the intracondylar notch) > ankle > wrist (small,square carpal bones) > hand > elbow > hip. Joint involvement is most often pauciarticular (between 2 and 4 joints) with JRA.

Radiographic features of JRA:

• soft tissue swelling
• periostitis
• epiphyseal overgrowth secondary to hyperemia
• premature closure of physis with associated growth retardation
• ankylosis/fusion of spine articulation (predominantly cervical spine ankylosis of the apophyseal joints)

Still's disease is an acute form of JRA that is associated with fever, rash, hepatosplenomegaly, and lymphadenopathy. Musculoskeletal involvement is rare in this JRA variant.