When compared to knee OA, the pseudosynovial tissue in TKA exhibit (1) elevation of alternative macrophage activation marker (CHIT1), chemokine (IL-8), and a proteolytic enzyme (MMP9); (2) downregulation of pro-inflammatory cytokine (TNF), osteoclastic regulator (OPG) and a stimulator of bone formation (BMP4); (3) no difference in IL-6, CCL3, CCL18, RANKL, DC-STAMP and SOCS3.