Pro-inflammatory cytokines such as TNFα, IL-1β and IL6, secreted by activated inflammatory synovial fibroblasts, are a major source of the inflammatory milieu in synovitis [109], and are central drivers of both articular cartilage degradation in OA through induction of MMPs and aggrecanases [105,110], and bone resorption in RA via the induction of RANK Ligand and subsequent activation of osteoclasts. Here, TNF is linked to rheumatoid arthritis.