Osteoarthritis is mainly characterized by cartilage degradation as a result of series of pathological processus still not well understood. In recent years much interest has centered on the contribution of cytokines to cartilage degradation: characterization of cytokines extracted from normal and pathological articulation, site of production (synoviocytes, chondrocytes, osteoblasts) and their role on the production of proteases, protease inhibitors or other types of molecules implicated in osteoarthritis. Several types of cytokines such as IL 1 beta and TNF alpha, known as proinflammatory factors in rheumatoid arthritis, have been shown to be present in the synovial fluid from osteoarthritic patients. Recent experimental data allow us to better understand the cellular and molecular mechanisms of the cytokines respectively involved into rheumatoid arthritis and osteo-arthritis.