Osteoarthritis is a complex disease involving not only the cartilage but also the adjacent bone and the synovial membrane. The etiology of osteoarthritis involves multiple factors. Unlike secondary forms of osteoarthritis, which are the result of other diseases or excessive mechanical stress, the origins of primary forms of osteoarthritis lie within the cartilage. In primary osteoarthritis complex interactions of cytokines leading to a derangement of homeostasis have been discovered, which lead to a slow and progressive degeneration of the cartilage and bone, ultimately resulting in destruction of the joint. Damage to the cartilage matrix is caused by an increased activity of matrix metalloproteases induced by catabolic cytokines. One of the initial events triggering these processes might be degenerative DNA alterations causing local defects in multiple genes leading to an impaired function of chondrocytes and a phenotype similar to senescence.
