Childhood arthritis: classification and radiology.

Childhood arthritis has now been reclassified into a single internationally recognized entity of juvenile idiopathic arthritis (JIA). Radiology provides an important role in the management of JIA, in helping in the differential diagnosis, monitoring disease progression and detecting complications. Traditionally, plain radiographs have been the imaging investigation of choice but magnetic resonance imaging (MRI) and ultrasound are now providing a more effective and safer alternative. The appropriate use of sequences in MR imaging is important in the early detection of joint abnormalities in JIA.