The book details the epidemiology, risk factors for the development of osteoarthritis, outlines modern views on its etiology and pathogenesis, presents methods for modeling the disease in an in vitro and in vivo experiment. Various classifications of osteoarthritis are given. The classification proposed by the Association of Rheumatologists of Ukraine takes into account the advantages and disadvantages of existing domestic and foreign classifications. Examples of diagnosis formulations are given. Both classical methods of diagnosing osteoarthritis (for example, radiological) and currently intensively developing - MRI, ultrasound, etc. are described in detail.