Figure 2.

Physiological, molecular, and metabolic alterations are responsible for the cause of osteoarthritis. CPII: type II collagen propeptide; C2C: neoepitope of type II collagen; Coll 2-1: 9-amino acid peptide of type II collagen (nitrated form Coll 2-1 NO₂); CTX: C-terminal telopeptide of collagen; PIIANP: N-propeptide IIA of type II collagen; PIICP: C-propeptide of collagen type II; COMP: cartilage oligomeric matrix protein; FSTL-1: follistatin-like protein 1; CRP: C-reactive protein; IL: interleukin; TNF: tumor necrosis factor; YKL-40: chitinase-3-like protein 1; ADMTs: A Disintegrin and Metalloproteinase with Thrombospondin motifs; MMP: matrix metalloproteinase; PTMs: posttranslational modifications; D-COMP: deaminated epitope of cartilage oligomeric matrix protein; NF-κB: nuclear factor kappa light chain enhancer of activated B cells; RANKL: receptor activator of NF-κB ligand; IFN-γ: interferon gamma; TLR4: toll-like receptor 4; MAPK: mitogen-activated protein kinase.