TNF and osteoarthritis: Much evidence supports the pathogenic role of pro-inflammatory (IL-1, IL-6, TNFα, IL-15, IL-17) and anti-inflammatory (IL-4, IL-10) cytokines in osteoarthritis (Kapoor et al., 2011; Wojdasiewicz, Poniatowski & Szukiewicz, 2014); however, the presence of a systemic inflammation in osteoarthritis has not been confirmed unanimously.