In the present study leptin was positively associated and SOCS-3 was negatively associated with MMP levels in SF in obese but not in non-obese patients with OA, further confirming the importance of the leptin-SOCS-3 axis in cartilage metabolism and its possible significance in obesity-induced OA. Here, SOCS3 is linked to obesity due to melanocortin 4 receptor deficiency.