Role of musculoskeletal ultrasound in juvenile idiopathic arthritis

Over the past decade, musculoskeletal ultrasound (MSK-US) has been described by many rheumatologists as the ‘stethoscope’ of the joint. Unlike conventional radiography, an established imaging technique for identifying progressive joint damage, US is sensitive to soft tissue lesions and can detect early erosive bone lesions [1,2]. The development of higher frequency probes (12–18 MHz) and portable US machines has led to better resolution of small joints and the increased use of MSK-US in patients with rheumatologic disease. Improvements in color Doppler (CD) and power Doppler (PD) imaging, where the amount of color is related to degree of blood flow, allow for better assessment of soft tissue inflammation [1,3,4]. Several studies have emerged supporting the clinical utility of MSK-US in evaluating rheumatologic diseases in children, especially in juvenile idiopathic arthritis (JIA), which will be described in this review. MSK-US is particularly well suited to the pediatric population in that it has no ionizing radiation, does not require sedation and can be easily performed in a clinical outpatient setting. Additionally, MSK-US allows for the dynamic assessment of clinically challenging joints and is relatively inexpensive compared with computed tomography (CT) or MRI [5,6]. JIA is the most common rheumatic disease in children and encompasses several types of chronic arthritis. JIA is a serious autoimmune disease that can cause significant short-term and long-term disability, including permanent joint damage [7]. Diagnosis of JIA is largely based on history and physical examination; however, imaging modalities including plain film radiography, CT, MRI and also MSK-US may play a role in diagnosing and managing JIA. Advances in MSK-US have led to more widespread interest among pediatric rheumatologists in the application of US to diagnose JIA and to monitor the effects of localized and systemic therapy. This article will review recent publications regarding the use of US in the diagnosis and treatment of JIA. Although the International League of Arthritis and Rheumatism (ILAR) classif ication is the most commonly used classification system for juvenile arthritis today, many of the research and published reports in childhood arthritis use terminology established by older classification criteria, such as juvenile chronic arthritis (JCA) and juvenile rheumatoid arthritis (JRA). All three classifications refer to chronic arthritis in children in which all other diseases are excluded [7]. This review article refers to the original classifications used in each study.