Transforming growth factor-β (TGF-β) is a multifunctional cytokine-induced ECM protein and was shown to contribute in the inducement of fibrosis [40]. This main fibrotic inducer was found to be elevated in the anterosuperior capsule of FS compared to nonspecific synovitis and was suggested to act as a constant stimulus for the induction of fibrosis in the joint capsule [33]. More importantly, the serum level of TGF-β was elevated in the serum of FS patients compared to control [41] and thus is suggested to be taken as a marker for FS development. This evidence concerns the gene TGFB1 and Feingold syndrome.