Single-cell RNA-seq analysis of cell types in the knee of healthy and OA patients. (a) UMAP plot of 6833 single cells from the human knee depicting 11 major cell types. Colours correspond to the clusters 0 to 10. (b) Bar plot shows frequency of each cell type in total, healthy, and OA groups. (c) Split UMAP plot depicting the clusters from healthy (N) and OA patients (O). (d) Heat map indicates the top 10 marker genes for each cell type. (e) Expression distribution of the top marker genes for the nonchondrocytes projected onto the UMAP plot: macrophages (MS4A7), endothelial cells (CDH5), and monocytes (HLA-DRA).