Can ultrasound help to overcome uncertainty in clinical joint assessment in juvenile idiopathic arthritis?

Objective Assessment of active synovitis is crucial for the management of juvenile idiopathic arthritis (JIA). We aimed to investigate the correlation of musculoskeletal ultrasound (MSUS) and clinical examination results and relate them to arthritis relapse rate. Methods JIA patients with questionable presence of active arthritis (Q-joints) and controls (JIA and healthy children) were recruited. MSUS of Q-joints, active joints and their inactive counterparts was performed at study entry. Standard disease activity parameters were prospectively recorded. Results Of 481 joints of 138 JIA patients, 99 joints (20.6%) of 58 patients had one or more Q-joints with 54/99 (54.5%) having MSUS features of active disease. Clinically inactive joints had lower proportion of MSUS synovitis (78/253, 30.8%) while MSUS activity was present in 114/129 (88.4%) of clinically active joints and in 2/105 (1.9%) joints of 36 healthy controls. Within the 15-month follow-up 23/99 (22%) Q-joints and 31/253 (12%) clinically inactive joints relapsed. Joints with subclinical synovitis relapsed more frequently than MSUS inactive ones (p<0.001). The relapse rate was higher in MSUS-active Q-joints (19/23, 82%) than in clinically inactive ones (16/31, 52%) with MSUS synovial hypertrophy as the main relapse predictor in multivariate analysis. Ankle and knee joints relapsed most frequently. Conclusion Acknowledgement of joints with questionable synovitis may contribute to the assessment of disease activity in JIA. Presence of MSUS synovitis carries a clinically meaningful risk of disease recurrence in these joints. In clinical practice, our findings encourage timely MSUS assessment of the joints in question, especially in patients without any other features of active disease.