The significance of MMP-9 for RA prognosis, particularly if they are determined in the early stages of the disease when we still cannot detect joint damage with the visualisation methods at our disposal, as well as the relationship between locally released and circulating MMPs and serological markers of RA (rheumatoid factor-RF and anti-citrulline protein antibodies-ACPA) have not been fully clarified yet. Here, MMP9 is linked to rheumatoid arthritis.