In this study, ten protein expressions (LAP3, DNAJB11, MANF, SCARA5, EIF3K, LCP1, CTSZ, C1orf123, PTPRC and EML4) were highlighted by LC-MS/MS as being present in the synovium from RA, but also from OA and CCPA patients; and were significantly increased or decreased in one of the three disease groups. This evidence concerns the gene PTPRC and rheumatoid arthritis.