If you’re trying to get motivated to lose weight, think about your knees.

The sheer numbers of knee replacement surgery have skyrocketed. In fact, the number of knee replacements has doubled in the past decade. More worrisome is that the number of knee replacement surgeries on patients younger than 65 has tripled in the same time frame.

There are some possibilities as to why this is occurring, including aging baby boomers as well as positive word of mouth and advertising regarding the surgeries.

But experts are circling around this theory: the increased obesity rate of middle age adults is driving the deterioration of our knees.

In a database called  Function and Outcomes Research for Comparative Effectiveness in Total Joint Replacement (FORCE-TJR), information is accumulated regarding total joint replacement surgeries from orthopedic surgeons in 22 states.

The latest data from FORCE-TJR revealed that younger patients were more likely to be obese than patients over age 65 who underwent knee replacement surgery. In fact, the average body mass index (BMI) of the middle age patients in the study was 33. A BMI of 33 falls into the obese range. Furthermore, this is the average BMI which means that roughly half of the participants have an even higher BMI.

Being overweight puts stress on all joints and can exacerbate osteoarthritis. Excess weight can cause an erosion of cartilage surrounding the knee. In addition, fat cells are believed to produce inflammatory cytokines that contribute to arthritis.

Overweight patients are particularly vulnerable to anterior knee pain, which is knee pain at the front of the knee. Anterior knee pain can include pain upon waking up, pain when walking after a sedentary period, difficulty walking up and down stairs, stiffness and soreness around the knee area and a general sensation of instability when standing upright.

Overweight patients may have other disease processes that can make a knee replacement surgery more complicated like diabetes, poor circulation and cardiovascular issues. Perhaps most troubling, some surgeons will not perform knee replacement surgery on morbidly obese patients, whose BMI is over 40.

Losing weight, even a fairly minimal amount can drastically reduce knee pain. An osteoarthritis study (the Framingham Study) showed that a 5% drop in weight among the participants improved joint pain by 18%.

One of the components to effective weight loss, of course, is increased exercise. Unfortunately for many patients with painful knees, some forms of exercise can be impossible. Physicians recommend swimming and water aerobics for these patients, as these exercises put far less stress on aching joints.

Please consult your health care team about any knee pain issues that you have and before you start any exercise regimen to alleviate them.