IntroductionOsteoarthritis (OA) is a kind of chronic, degenerative disorder with unknown causes. In this study, we aimed to improve our understanding of the gut microbiota profile in patients with knee OA.Methods16S rDNA gene sequencing was performed to detect the gut microbiota in fecal samples collected from the patients with OA (n= 32) and normal control (NC,n= 57). Then the metagenomic sequencing was used to identify the genes or functions linked with gut microbial changes at the species level in the fecal samples from patients with OA and NC groups.ResultsThe Proteobacteria was identified as dominant bacteria in OA group. We identified 81 genera resulted significantly different in abundance between OA and NC. The abundance ofAgathobacter,Ruminococcus,Roseburia,Subdoligranulum, andLactobacillusshowed significant decrease in the OA compared to the NC. The abundance of generaPrevotella_7,Clostridium,FlavonifractorandKlebsiellawere increasing in the OA group, and the familiesLactobacillaceae,Christensenellaceae,Clostridiaceae_1andAcidaminococcaceaewere increasing in the NC. The metagenomic sequencing showed that the abundance ofBacteroides stercoris,Bacteroides vulgatusandBacteroides uniformisat the species level were significantly decreasing in the OA, and the abundance ofEscherichia coli,Klebsiella pneumoniae,Shigella flexneriandStreptococcus salivariuswere significantly increased in OA.DiscussionThe results of our study interpret a comprehensive profile of the gut microbiota in patients with knee OA and offer the evidence that the cartilage-gut-microbiome axis could play a crucial role in underlying the mechanisms and pathogenesis of OA.