Purpose: Diagnosis of juvenile idiopathic arthritis (JIA) remains difficult due to unspecific clinical and laboratory findings, especially in early stages of the disease. The purpose of our study was to determine the sensitivity and specificity of MR imaging in diagnosing JIA of the knee joints.
Material and methods: Forty children (3-17 years old) clinically diagnosed with JIA (follow-up > 1 year) of a knee joint and a control group of 40 children with painful knee joints (MR diagnosis: bone bruise of the knee (n = 7), normal knee joint (n = 12), osteomyelitis (n = 6), septic arthritis (n = 2), bone tumor (n = 7) and miscellaneous bone lesions (n = 6)) were examined using a 1.5 T MR unit. T1-weighted spin-echo (SE), T2-weighted fast SE, contrast-enhanced T1-weighted SE and 2D gradient echo sequences were performed. The receiver operating characteristic (ROC) curves evaluation was conducted by 5 independent radiologists.
Results: The positive criteria for diagnosing JIA were joint effusions (n = 40), contrast-enhancing synovitis (n = 39), cartilage lesions (n = 15), subchondral erosions and bony destruction (n = 1). Sensitivity and specificity were 93.5% and 92.5%, respectively. Both cases of septic arthritis were misdiagnosed as JIA by all radiologists.
Conclusion: Contrast-enhanced MR imaging seems to be a highly sensitive tool in establishing the diagnosis of JIA.