Clinical settings in knee osteoarthritis: Pathophysiology guides treatment.

Osteoarthritis (OA) is the most common chronic joint disorder and its prevalence increases rapidly during midlife. Complex interactions of genetic alterations, sex hormone deficit, and aging with mechanical factors and systemic inflammation-associated metabolic syndrome lead to joint damage. Thus, the expression of a clinical phenotype in the early stages of OA relies on the main underlying pathway and predominant joint tissue involved at a given time. Moreover, OA often coexists with other morbidities in the same patient, which in turn condition the OA process. In this scenario, an appropriate identification of clinical phenotypes, especially in the early stages of the disease, may optimize the design of individualized treatments in OA. An ESCEO-EUGMS (European Union Geriatric Medicine Society) working group has recently suggested possible patient profiles in OA. Hereby, we propose the existence of 4 clinical phenotypes - biomechanical, osteoporotic, metabolic and inflammatory - whose characterization would help to properly stratify patients with OA in clinical trials or studies. Further research in this field is warranted.