Synovial membrane is a thin tissue that lines the diarthrodial joints.
Consists of a lining layer only a few cells thick with fibroblast like synoviocytes and macrophages which produce synovial fluid and extracellular matrix, and a sublining layer of loose connective tissue.
With rheumatoid arthritis the lining layer has an increased in the number of cells and the sublining is infiltrated with inflammatory cells, including lymphocytes, mast cells and macrophages.