revealed that synovial tissue from RA patients exhibited a 3.5-fold increase in CD44 expression compared to that from osteoarthritis patients, and a 10.7-fold increase compared to patients with joint trauma but without chronic arthritis, suggesting a significant upregulation of CD44 in the synovial cells of RA patients, with the expression levels of CD44 in synovial tissue being associated with the intensity of inflammation [52]. Here, CD44 is linked to rheumatoid arthritis.