It is suggested that rheumatoid atrhritis is the result of a number of mechanisms affecting to the synovial tissue. The changes in synovial membrane of the knee joints were examined in dogs with rheumatoid arthritis by light microscopic.

In this study, we evaluated changes in synovium. Tissue samples were taken from synovial membrane of dogs with rheumatoid arthritis . We found that the intimal and subintimal layer of the synovium, were heavily infiltrated by mononuclear cells mast cells. Hence, the synovial hyperplasia was also found. Increased numbers of mast cells mostly degranulated were present in the synovial tissue. Synovial membrane was containing fibrin clot materials.