Previously, researchers found that in the osteoarthritis group, patients had significantly higher levels of complement components (C4d, C3bBbP and sTCC) than in the normal group, median levels increased by fourfold, twofold and fourfold, respectively.[103] Furthermore, molecules of the cartilage ECM, including fibronectin, aggrecan and cartilage oligomeric matrix protein (COMP), have been proven to activate the complement system to exacerbate synovial inflammation.[104, 105, 106]. Here, COMP is linked to osteoarthritis.