Objective : Given that the PI3K/AKT/mTOR signaling pathway is associated with the progression of knee osteoarthritis (KOA) , this study aims to investigate whether the polarization induction of synovial macrophages mediated by the PI3K/AKT/mTOR signaling axis is the cause of KOA progression . Methods : The synovial fluid of KOA KL-Ⅱ and KL-Ⅲ patients and normal individuals was collected , and the percentage of M1 macrophages (CD80 , CD86) and M2 macrophages (CD163 , CD206) in the synovial fluid (M1 /M2 ratio) was measured to e- valuate the polarization of macrophage cytokines such as IL-1 , IL-6 , IL-10 , and tumor necrosis factor (TNF) -α, transforming growth factor ( TGF)-βExpression in KOA synovial fluid , and detect and analyze of key molecules PI3K/AKT/mTOR signaling axis PI3K , AKT3 , mTORC1 , and inducible nitric oxide synthase ( iONS) in KOA synovial fluid . Results : Compared with the synovial fluid of normal individuals , the percentage of M1 macrophages (CD80 , CD86) in KOA patients increased (P < 0. 01) , and the M1 /M2 ratio increased ( P < 0. 001) ; The ex- pression of IL-1 , IL-6 , and TNF-αin the synovial fluid of the KOA group was also higher than that of the control group (P < 0. 01) , while the expression of IL-10 and TGF-βin the KOA group was significantly reduced ( P < 0. 01) ; The key proteins PI3K , AKT3 , mTORC1 , and downstream inflammatory factor iONS in the PI3K/AKT/ mTOR signaling pathway in the synovial fluid of the KOA group were higher than those in the control group (P < 0. 01) . Conclusion In KOA synovial fluid , M1 macrophage polarization plays a dominant role , and the inflam- matory response mediated by M1 macrophage polarization may be the cause of synovitis . At the same time , the PI3K/AKT/mTOR signaling pathway may mediate the polarization of M1 macrophages involved in KOA inflammato- ry response .