TNF and osteoarthritis: OA is a degenerative joint disease determined by the imbalance of pro-inflammatory and anti-inflammatory mediators such as IL-1α, IL-1β, IL-4, IL-6, IL-8, IL-10, IL-11, IL-13, IL-15, IL-17, TNF-α, leukocyte inhibitory factor, IL-1 receptor antagonist, matrix metalloproteinases, proteases, chemokines, nitric oxide, prostaglandins, and leukotrienes [7,8].