The aim of the present study was to verify the over-expression of KIAA1199 mRNA and protein in the serum, synovial fluid and synovial tissues obtained from patients with active and inactive RA and healthy controls, explore the effect of KIAA1199 on FLSs proliferation and angiogenesis by MTT, cell migration, tube formation and chorioallantoic membrane (CAM) assay after KIAA1199 knockdown and over-expression. The gene discussed is CEMIP; the disease is rheumatoid arthritis.