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Figure 1: Physiopathology of osteoarthritis. IL: interleukin; TNF: tumoral necrosis factor; NO: nitric oxide; PG: prostaglandins; MP: metalloproteases; LIF: leukemia inhibitory factor. Targets of diverse pathophysiologic factors of osteoarthritis include not only articular cartilage but also several structures of the articular surface, where an unbalance favoring catabolism occurs, with degradation of extracellular matrix. This process is triggered by numerous proinflammatory and proteolytic molecules which generate a local vicious circle. (Refer to text.)