Biomechanical factors support the osteophyte development.29 One of the mechanisms of articular cartilage damage is stiffness of subchondral bone, if the bone becomes stiffer; it may be less able to absorb impact loads, which may in turn lead to increased stresses in the cartilage.28 Softening of articular cartilage in the patella, frequently described as chondropathy or chondromalacia of the patella, causes to erosion of the cartilage.30 Although chondromalacia of the patella is a common phenomenon, its aetiology is unclear; in addition to several functional and morphological changes in OA, studies has shown different inflammatory mediators, CCI 779 proteinases, Cell proliferation,

biochemical parameters in development of disease.31 Chondrocytes are the only cells in cartilage responsible for synthesis and breakdown of matrix which regulated by cytokines

and growth factors, under arthritis condition their balance may be disturbed.32 Cytokines which have an impact on articular cartilage metabolism are classified in three groups including, catabolic (IL1α, IL1β, TNF α), regulatory and enzyme inhibitory (IL-6, Il-8, IL-4, IL-10, IFNγ) and anabolic (Growth factors, IGF, COMPs, TGF β).33 It is generally accepted that IL-1 is the key cytokine at early and late stages of OA; the interleukin-1 (IL-1) family includes two agonists, check details IL-1α and IL-1β, are produced by two different genes34 and a specific receptor antagonist, IL-1Rα.35 Interleukin-l is a multifunctional pro inflammatory cytokine that affects most cell types and results in several effects including lymphokine production, cartilage breakdown, interfering with the activity of growth factors such as insulin-like growth factor, or decreasing the synthesis of key matrix components such as aggregan and proliferation

of fibroblast have a crucial role in arthritis disease.35 and 36 The presence of activated macrophages will release the IL which has a role in destruction of cartilage.37 NF- kβ (nuclear factor kappa-light-chain-enhancer of activated B cells) is nearly one of the key regulatory mechanisms involved in regulating and controlling expression of cytokines are critical in immune function, inflammation.38 It is known that stimulus of NF-kβ leads to expression of TNFα and IL1β.39 and 40 The TNF superfamily is a group of cytokines with important functions in immunity and inflammation, among these, TNF α is effective proinflammatory cytokine that plays an important role in inflammation, and matrix degradation by stimulating proteolytic enzyme secretion from chondrocytes and synovial fibroblasts.41 TNF induces fever initially by increasing prostaglandin E2synthesis in the hypothalamus and subsequently production of IL-1and IL6.