More detailed examination of fibroblast-like synoviocytes (FLSs) in OA and RA will reveal more about the mechanistic differences between synovitis in these two diseases, but we already know that NF-κB signaling and tumor necrosis factor α (TNF-α) are also important in synovitis in OA49. This evidence concerns the gene NFKB1 and rheumatoid arthritis.