Integrins and ligand–receptor interactions between integrins play a significant role in binding to multiple extracellular ligand proteins, regulating cell differentiation and proliferation, and maintaining cartilage homeostasis in chondrocytes, while CD44 may mediate inflammatory processes; in addition, the CD44 level in articular cartilage is related to OA and rheumatoid arthritis (RA) disease degree and joint destruction (16, 20). The gene discussed is CD44; the disease is rheumatoid arthritis.