Abnormal ultrasonography findings were common in children with clinically inactive juvenile idiopathic arthritis (JIA; n = 40) but did not correlate with disease flares during up to 2 years of follow-up in a single-centre study. At baseline, 45% of the patients had at least one abnormal finding on ultrasonography. These baseline findings had a sensitivity of 15% and a positive predictive value of 12% when evaluated against clinical flares at the individual joint level during follow-up.