Abstract:

Macrophage polarization is involved in the entire process of the occurrence and development of knee osteoarthritis（KOA）. By polarizing into distinct functional phenotypes， macrophages play key regulatory roles in the initiation of inflammation， matrix degradation，suppression of cartilage formation，and progression of the disease. The M1-type macrophages secrete numerous pro-inflammatory cytokines to exacerbate the inflammatory responses and promote the destruction of articular cartilage. Conversely， the M2-type macrophages help maintain the extracellular matrix homeostasis and facilitate cartilage formation by releasing anti-inflammatory factors while suppressing the secretion of inflammatory factors，thereby exerting anti-inflammatory effects and promoting tissue repair. Recent studies have shown that an imbalanced ratio of M1/M2 macrophages（M1/M2 ratio） is closely linked with both the pathogenesis and progression of KOA. Restoration of the dynamic balance between these two subtypes could be an essential strategy for treating and preventing KOA. This article reviewed the current literatures retrieved from PubMed and CNKI databases using the keywords “knee osteoarthritis” and “macrophages” over the past decade. The review introduced the process of macrophage polarization and the mechanisms of different macrophage phenotypes in KOA， and further discussed the recent advances in modulating the M1/M2 ratio for KOA management through chemical drugs， bioactive molecules， and traditional Chinese medicine and so on， aiming to provide the theoretical insights for future research and clinical interventions.

Key words: Knee osteoarthritis, Macrophage, M1-type macrophage, M2-type macrophage, M1/M2 ratio