IL6 and obesity due to melanocortin 4 receptor deficiency: One of hypothesis that possible explain the link between obesity and OA is the metabolic theory.25,26The reason is that pro-inflammatory factors mainly released by abdominal and visceral fat tissue, such as c-reactive protein (CRP), interleukin 6 (IL-6) and Plasminogen activator inhibitor type 1 (PAI-1), would adversely affect joint structure and accelerate development of OA.13,30