Kriegova E, et al. - Authors ascertained the immune cell composition in synovial fluids (SFs) from knee osteoarthritis (OA) and in subgroups according to gender. Distinct phenotypes (monocyte- and lymphocyte-predominant) within each gender group were revealed with data mining analysis based on the immune cell composition of SFs. Marked differences between male and female patients were demonstrated in this first study on the cellular complexity of SFs in knee OA. A rational starting point for patient stratification according to their phenotypes, as was required for phenotype-specific treatment strategies was noted in the findings.The findings give a rational starting point for patient stratification according to their phenotypes, as was required for phenotype-specific treatment strategies.