The evolving role of obesity in knee osteoarthritis

Purpose of review The frequency of knee osteoarthritis continues to accelerate, likely because of the increasing proliferation of obesity, particularly in men and women 40-60 years of age at the leading edge of the 'baby boom' demographic expansion. The increasing pervasiveness of obesity and the growing appreciation of obesity's accompanying metabolic/inflammatory activities suggest rethinking the knee osteoarthritis paradigm. Recent findings Whereas once knee osteoarthritis was considered a 'wear-and-tear' condition, it is now recognized that knee osteoarthritis exists in the highly metabolic and inflammatory environments of adiposity. Cytokines associated with adipose tissue, including leptin, adiponectin, and resistin, may influence osteoarthritis though direct joint degradation or control of local inflammatory processes. Further, pound-for-pound, not all obesity is equivalent for the development of knee osteoarthritis; development appears to be strongly related to the co-existence of disordered glucose and lipid metabolism. Additionally, obesity loads may be detected by mechanoreceptors on chondrocyte surfaces triggering intracellular signaling cascades of cytokines, growth factors, and metalloproteinases. Summary This review summarizes recent literature about obesity, knee osteoarthritis and joint pain. Consideration of adipocytokines, metabolic factors, and mechanical loading-metabolic factor interactions will help to broaden the thinking about targets for both prevention and intervention for knee osteoarthritis.