Our flexible joints are synovial joints composed of bone, hyaline cartilage, synovial membrane, ligaments and tendons. Rheumatoid arthritis is a disease that affects multiple synovial joints and involves inflammation of the synovial membrane, often resulting in loss of function due to erosion of bone and cartilage. Inflammation is accompanied by an influx of immune-competent cells and by aberrant proliferation of resident fibroblast-like synoviocytes. Accretion of fibroblasts directly contributes to joint destruction, through enhanced production of matrix-degrading enzymes, and indirectly, through excessive release of cytokines that boost the immune system. Targeting the proliferative fibroblast could facilitate regeneration of synovial joints.