Weight gain and knee pain? Has putting on extra pounds made your knees hurt? What causes your knees to hurt when you gain weight is a two part answer. First, the mechanical effects of the increased weight on the knees take their toll and second the other effects of weight gain (metabolic) have impacts on cartilage as well. It makes sense that more weight equals more wear and tear. How much? Each pound you gain increases the forces on the knee four fold. So loosing a pound would have the opposite effect (taking off four times as much weight from your knees when you walk). However, there’s another big factor at play here as well, the changes to the insulin system in patients who are overweight. We know for example that blood sugar control problems, like those seen in patients with Metabolic Syndrome chew up cartilage. We also know that patients who are heavier with high blood pressure and insulin problems (metabolic syndrome) have worse knee and hip replacement outcomes. A recent study adds fuel to this data, showing that heavier women have more arthritis in both knees over time. This study didn’t show the same association between one sided knee arthritis and weight, likely because the patients who had injured one knee would eventually develop arthritis regardless of weight.The fact that the arthritis in heavier women was seen in both knees would suggest that the effect is due to some bigger process (see insulin discussion above). The upshot? Taking off even a few pounds may make a difference. In addition, consider going on a low glycemic diet to help reduce the effects of a metabolic syndrome. Diets out there that seem to work are The Zone, Atkins, and the South Beach Diet. Loosing weight, based on this study and others, may help save your knees from knee replacement!