Comparative Research Between Rheumatoid Arthritis And Osteoarthritis Of The Knee In MRI And Histopathology

Objective:To analyze and compare the MRI characters between rheumatoid arthritis and osteoarthritis of the knee, finding out the differences between rheumatoid arthritis and osteoarthritis. By the comparative study of histopathology corresponding with MRI, exploring the pathological mechanism of articular cartilage, subchondral bone and meniscus damage preliminary.Material and Methods:40knees in33patients with rheumatoid arthritis and60knees in58patients with osteoarthritis was examined by MR and all of the images were analyzed. To statistics the incidence and the extent of lesions at aspects of articular cartilage, subchondral bone, meniscus and synovium in knee joints, and compare differences between rheumatoid arthritis and osteoarthritis. Meanwhile,8knees in6patients with rheumatoid arthritis and10knees in10patients with osteoarthritis was treated by total knee arthroplasty (TKA) and was examined by histopathology, and to observe the characteristics of histopathology corresponding with MRI.Results:1.Comparison of the articular cartilage:There was no statistical significance of the articular cartilage injure between medial tibiofemoral joints and lateral tibiofemoral joints in the knee rheumatoid arthritis (P>0.05). The articular cartilage injure of medial tibiofemoral joints was significanily higher than lateral tibiofemoral joints in the knee osteoarthritis (P<0.01). There was no statistical significance of the articular cartilage injure of medial tibiofemoral joints and patellofemoral joints between rheumatoid arthritis and osteoarthritis(P>0.05). The articular cartilage injure of lateral tibiofemoral joints in the knee rheumatoid arthritis was significanily higher than in the knee osteoarthritis (P<0.01). The affected area of articular cartilage was an average of4.68/cases in the knee rheumatoid arthritis, and3.3/cases in the knee osteoarthritis. The affected area of articular cartilage in the knee rheumatoid arthritis was significanily higher than in the knee osteoarthritis(P<0.01).2.Comparison of the subchondral bone marrow:There was no statistical significance of the subchondral bone marrow lesions between medial tibiofemoral joints and lateral tibiofemoral joints in the knee rheumatoid arthritis (P>0.05). The subchondral bone marrow lesions of medial tibiofemoral joints was significanily higher than lateral tibiofemoral joints in the knee osteoarthritis(P<0.01). There was no statistical significance of the subchondral bone marrow lesions of patellofemoral joints between rheumatoid arthritis and osteoarthritis (P>0.05). The subchondral bone marrow lesions of medial and lateral tibiofemoral joints in the knee rheumatoid arthritis was significanily higher than in the knee osteoarthritis (P<0.05). The affected area of subchondral bone marrow lesions was an average of3.18/cases in the knee rheumatoid arthritis, and2.27/cases in the knee osteoarthritis. The affected area of subchondral bone marrow lesions in the knee rheumatoid arthritis was significanily higher than in the knee osteoarthritis(P<0.01).3.Comparison of the articular cartilage with subchondral lesions:The subchondralbone marrow lesions was often occurred with the articular cartilage injured. The injured articular cartilage (grade Ⅰ-Ⅳ) with subchondral bone lesions in the knee rheumatoid arthritis was significanily higher than in the knee osteoarthritis(P<0.05). In the knee rheumatoid arthritis, there were55%(22/40) cases having the mildly injured articular cartilage (including grade Ⅰ and Ⅱ).4.Comparison of the menisci:There was no statistical significance of the menisciinjured between medial and lateral in the knee rheumatoid arthritis (P>0.05). The injure of medial menisci was significanily higher than lateral in the knee osteoarthritis(P<0.01). The injure of medial and lateral menisci in the knee rheumatoid arthritis was significanily higher than in the knee osteoarthritis(P<0.01).5.Comparison of the synovium:In the knee rheumatoid arthritis, there were97.5%(39/40)cases having diffuse synovial thickening, including20cases with bone destruction in the bare area. In the knee osteoarthritis, there were21.7%(13/60) cases having synovial thickening, with limited location, none of them had bone destruction in the bare area.Conclusions:1.In this study, we found the articular cartilage of knee rheumatoid arthritis was not completely destroyed but the subchondral bone marrow was injured, which had challenged the past viewpoint that the subchondral bone was destroyed by synovial pannus directly. It may be because the subchondral bone was attacked by body’s immune system firstly, and the articular cartilage was damaged subsequently.2.1n the knee rheumatoid arthritis, the articular cartilage, subchondral bone marrow, menisci was damaged of wide area and severe extent and the synovial thickening was distributed widely in various areas of knee joint capsule. The articular cartilage and subchondral bone marrow of medial and lateral tibiofemoral joints were damaged consistently in the knee rheumatoid arthritis, which may be relate to the destruction of menisci.3.In the knee osteoarthritis, the articular cartilage, subchondral bone marrow, menisci was damaged locally and the synovial thickening was distributed locally also. The medial tibiofemoral joints and the medial menisci was often injured.4.Pathological changes of articular cartilage, subchondral bone, menisci and synovial was different between knee rheumatoid arthritis and osteoarthritis. Pathological changes of advanced stage of knee rheumatoid arthritis was often occurring concurrently with pathological changes of knee osteoarthritis. Therefore, MRI can reflect the pathological changes in general, and it is the non-invasive and effective examination methods to distinguish knee rheumatoid arthritis from osteoarthritis.