MRI manifestation of the knee in juvenile idiopathic arthritis and clinical relevance

Abstract

Objective To semi-quantitatively assess the MRI manifestations of knee in patients with juvenile idiopathic arthritis (JIA) and to explore the relationship between the semi-quantitative scores with clinical inflammatory biomarkers. Methods Fifty children diagnosed as JIA and presented with knee pain, swelling or limitation were enrolled and their clinical and imaging findings were retrospectively analyzed. Contrast-enhanced MRI scan of the knee were performed in all cases (a total of 50 knees). MRI abnormalities, including synovial hypertrophy, joint effusion, bone marrow edema, joint cartilage injury and bone erosion, were assessed with a semi-quantitative score system. The erythrocyte sedimentation rate (ESR) and C reactive protein (CRP) at the same period with MRI were collected. The relationships between the MRI scores and laboratory biomarkers (CRP and ESR) were analyzed with Spearman correlation analysis. Results In MR images of all the 50 knees with JIA, synovial hypertrophy (43, 86%) and joint effusion (40, 80%)were major abnormalities, bone marrow edema was seen in 6 knees, joint cartilage injury in 12 knees and no bone erosion was seen. The scores of synovial hypertrophy, joint effusion, marrow edema, joint cartilage injury and bone erosion were 7 (0- 12), 3 (0- 7), 0 (0- 6), 0 (0- 10), 0, respectively. There was significant correlation between synovial hypertrophy and joint effusion (r=0.719, P=0.001). There were positive relationship between synovial hypertrophy and ESR and CRP (r=0.306 and 0.285; P=0.031 and 0.043, respectively).Other indexes had no significant relationship with ESR or CRP. Conclusions MRI could comprehensively evaluate knee involvement in patients with JIA. Joint effusion could be a useful reference to evaluate the condition of synovitis for pediatric patients with non-enhanced MR images. Key words: Arthritis ,juvenile rheumatoid; Magnetic resonance imaging; Knee joint