Comparison between rheumatoid arthritis and osteoarthritis on knee joint MRI

Objective: To compare the MRI characteristics between the late stage rheumatoid arthritis (RA) and osteoarthritis (OA) in the knee joints. Materials and Methods: We collected knee joints MR data using 0.35 T MR from 40 patients with rheumatoid arthritis and 60 cases with osteoarthritis between July, 2010 and August, 2012. We compared the differences in the menisci, the articular cartilage, the subchondral bone, and synovial lesions between the two groups. We calculated the morbidity and analyzed the severity in each part in both groups, and compared the differences between the two groups. If P<0.05, the results had statistical significance. Results: The injury of all parts in the medial and lateral menisci in the RA group was more severe than in the OA group (P<0.05). The articular cartilage of lateral tibiofemoral joints in the RA group was more severe than in the OA group (Z values of the lateral femoral condyle and the lateral tibial plateau were 5.702 vs. 7.534, P<0.05). However, the injury did not significantly differ at the articular cartilage in the patellofemoral joints and in the medial tibiofemoral joints (P>0.05). The subchondral bone marrow lesions of both medial and lateral tibiofemoral joints in the RA group were more severe than in the OA group (the χ² values of the medial and lateral femoral condyle were 6.730 and 23.938, respectively; the χ² values of the medial and lateral tibial plateau were 12.033 and 41.017, respectively; P<0.05). However, there was no statistical significance in the subchondral bone marrow lesions in the patellofemoral joints (P>0.05). In the RA group, there were 97.5% (39/40) cases having diffuse synovial thickening, including 20 cases with bone destruction in the bare area. In the OA group, there were 21.7% (13/60) cases having synovial thickening with less extend compared to RA group, none of them had bone destruction in the bare area. Conclusions: There are diffuse synovial thickening, bare area destruction, diffuse injure of both menisci. and diffuse articular cartilage and subchondral bone marrow lesions in the patients with RA. However, the synovial thickening is local, the body and the posterior horns of the medial menisci are more easily to be injured, and the medial tibiofemoral joints and the patellofemoral joints are more vulnerable to degenerate in the patient with OA. (authors)