Objective To investigate the arthroscopic presentations of knee joint of rheumatoid arthritis (RA). Methods During December 2005 to February 2008,223 patients with RA in our department underwent knee arthroscopy examination. The arthroscopic presentations of 310 knee joints were analyzed retrospectively. Results Synovial hyperplasia were observed in 305 knees (98.4% ) out of 310 ones. The medial part (88.4%), intercondylar fossa (86.1%) and lateral space (83.2%) were the most frequent localization of synovial hyperplasia, which was less common in the suprapatellar bursa. Hyperplastic synovium of 296 knees had coralloid or cotton-wool like presentation, with central nourishing vessels. Nine knees were lichen-like hyperplasia, without nourishing vessels. Different degrees of pathological changes or defect could be seen in 301 knees, including merely cartilage degeneration in 63 knees, cartilage degeneration plus cartilage damage or defect in femoral medial condyle or lateral condyle in 124, 163 knees, in which 53, 45 with the damage deep to the cancellous bone. Most anterior or posterior cruciate ligament (in 274 knees) were covered with hyperplastic synovium, anterior cruciate ligament of 51 knees were partial ruptured, 5 ones were completely ruptured,while 23 and 1 case had these presentations in the posterior cruciate ligament.. Meniscus damage was commonly seen under arthroscope. 234 and 38 knees had medial meniscus torn or disappeared completely, while 214 and 45 in the lateral meniscus. Conclusion Synovial hyperplasia is commonly seen in knee joints of RA and most commonly seen in the intercondylar fossa, medial space and lateral space, but less common in the suprapatellar bursa. The hyperplastic synovium appears most often in the coralloid or cotton-wool like form, Cartilage damage is commonly seen in knee joints of RA. The most serious damage of the cartilage is seen in the femoral medial condyle or lateral condyle. Partial or complete anterior cruciate ligament rupture can be seen in one proportion of knees. In most knees of RA, meniscus are torn or disappeared mostly or completely.