Imaging in juvenile idiopathic arthritis with a focus on ultrasonography

Early therapeutic intervention and use of new highly efficacious treatments have improved the outcome in many patients with juvenile idiopathic arthritis (JIA), but have also led to the need for more precise methods to evaluate disease activity. In adult rheumatology, numerous studies have established the importance of magnetic resonance imaging (MRI) and ultrasonography (US), and MRI is considered the reference standard. Nevertheless, due to differences in disease characteristics and the unique features of the growing skeleton, the findings obtained in adults are not directly applicable to children and adolescents. For paediatric patients, US offers specific advantages over MRI, because it is non-invasive, does not require sedation or general anesthesia (which facilitates repeated examinations for follow-up), is quickly accessible bedside, and is easy to combine with clinical assessment (interactivity). Agitation of the patient is rarely a problem, and hence young children can be seated on a parent's lap or play while being examined, and multiple locations can be assessed during a single session. Furthermore, modern high-frequency US transducers used by experienced US examiners can provide unsurpassed resolution of the superficial musculoskeletal structures in children. US is also the best available technique for imaging guidance of steroid injections. Unfortunately, there are still no validated MRI or US scoring systems for evaluating inflammatory and joint damage abnormalities in JIA, and few US studies have been conducted. Sonographic assessment of disease activity has, however, been proven to be more informative than clinical examination and is also readily available at points of care. This review summarises the literature on imaging in JIA, focusing on US and the important role this technique will play in JIA in the future.