Resistin levels are higher in obese persons and in patients with severe knee OA.58 Moreover, resistin may lead to an overexpression of MMPs.28,29 Hence, a decrease in resistin (and MMP-9) levels elicited by daily activities such as walking may be particularly relevant in patients with OA and/or obesity. This evidence concerns the gene RETN and obesity due to melanocortin 4 receptor deficiency.