Objective By comparing the MRI findings of menisci, articular cartilage, and subchondral bone marrow of knee joints with pathological characteristic in patients with rheumatoid arthritis (RA), to explore the MR characteristics and underlying mechanisms in RA knee joints. Methods Between 2008 and 2014, 13 knee joints in 11 patients with RA, who had total knee arthroplasty, were included in the study, the degree of destructions of articular cartilage, bone marrow, menisci of knee joints were evaluated on MR images and pathological slices. When the pathologist was uncertain about the cell origin, the immunohistochemistry was done to identify the cell origin. We analyzed the degree of injury of articular cartilage and menisci,as well as the degree of injury of the pathological manifestations of subchondral bone, articular cartilage and menisci. We also compared the degree of pathological manifestations of the bone marrow edema under and distant from the bare area, using Mann-Whitney U test. Results The articular cartilage destruction were level 4 and menisci damage were level 4 on MRI in most patients. Totally 52 locations presented bone marrow edema on MRI, 18 of 52 (34.6%) sites of bone marrow edema were covered by cartilage and distant from bare area, while 34 of 52 (65.4%) sites located under the bare area.Fibrosis, mosaic structure, and lymphocytes infiltration were the most common changes in bone marrow with edema. There was no significant difference in severity of pathological findings between the edema areas under and distant from areas with damaged articular cartilage. For articular cartilage damage, fibrosis and thinning of the cartilage, and cartilage hyperplasia were the most common pathological changes. 5 of 26 (19.2%) menisci were found in resected samples, all the menisci showed atrophy, thinning, and heterogeneous intensityon MR. Fibrosis, engulfing calcified debris and fibrinoid necrosis were most commonly seen in menisci samples. Conclusion The menisci and articular cartilage are severely destroyed in patients with RA at late stage, bone marrow edema can be found at bare areas and areas distant from bare areas. RA in knee joints can involve several structures simultaneously, resulting in joint function decreased severely even disability.%目的：通过对膝类风湿关节炎（RA）病人关节软骨、软骨下骨髓及半月板进行MR-病理对照分析，探讨膝RA的MRI特点及病变发生机制。方法收集我院2008年11月—2014年12月间确诊为膝RA并行全膝关节置换术的11例病人（共13只膝关节）资料。评价关节软骨、软骨下骨髓及半月板的MRI表现，并在显微镜下对观察膝RA病人膝关节各部位组织的病理学特点。当细胞成分不确定时，使用免疫组织化学方法确定细胞种类。对关节软骨损伤MRI分级和半月板损伤MRI分度以及不同部位关节软骨下骨髓水肿和关节软骨、半月板损伤的病理学表现分度进行分析，并采用Mann-Whitney U检验对位于裸区和远离裸区的软骨下骨髓水肿的病理学表现分度进行比较。结果本组膝RA病人中大部分病人的MRI关节软骨破坏程度为4级，半月板破坏程度为4度。 MRI显示52处软骨下骨髓水肿的部位中有18处（34.6%）于骨髓水肿上方覆盖有关节软骨且远离裸区，而34处（65.4%）的骨髓水肿位于裸区且邻近滑膜。在软骨下骨髓水肿的病理学表现中，纤维化、骨小梁镶嵌样结构及淋巴细胞浸润为最常见的表现。位于裸区和远离裸区骨髓水肿的两组间各种病理学表现分度差异均无统计学意义（均P＞0.05）。在关节软骨破坏的病理学表现中，纤维环、关节软骨破坏变薄及关节软骨增生为最常见的镜下病理表现。在全部13只切除的膝关节共26个半月板标本中，仅发现5个（19.2%）残留半月板标本，在MRI上均表现为萎缩、变薄，信号不均，其最常见的病理学表现为纤维化和吞噬包裹钙化碎片。结论晚期膝RA病人半月板及关节软骨破坏严重，骨髓水肿可发生于关节裸区或远离裸区部位，提示膝RA可同时累及多个部位，导致病人关节功能严重减退甚至丧失。
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