Gomez-Aristizabal A, et al. - Researchers assessed synovial fluid leukocytes (SFLs) and peripheral blood mononuclear cells from subjects with knee osteoarthritis (OA) to estimate the synovial fluid monocyte/macrophage subsets and their relationship with patient-reported consequences in OA cases. They noted the abundance of SF MΦs subsets among SFLs. They found a correlation of MΦ subset ratios with PROMs, especially stiffness, function, and quality of life. All SF MΦs revealed high levels of HLA-DR implying an activated phenotype. An association between OA SF MΦ subsets and activated CD4⁺ T cell subsets was observed which indicated the modulation of CD4⁺ T cell activation by MΦs.