James Joseph, Jr., MD
Orthopaedic & Sports
Medicine at Cypress, LLC
316-219-8299
www.osmcypress.com
Obesity’s Effects on Bones and Joints
“A 200 lb person puts about 600 lbs. of pressure on their knees just by walking.”
Obesity is an escalating health threat in the United States, and has many wide-reaching effects on health. It increases the risk of developing life-shortening conditions including heart disease, stroke, diabetes, sleep apnea and cancer. However, one effect of obesity that is not discussed as much, is the effect excessive weight has on your joints and the musculoskeletal system.
Obesity is generally defined as being more than thirty percent above one’s ideal body weight. The rate of obesity is increasing across all demographic groups in the U.S. and is especially high in children. While many factors are to blame, certainly poor diets, fueled by processed and fast foods, and sedentary lifestyles are culprits.
Joint and Spinal Problems
Obesity accelerates the wear on the joints and spine. In particular, osteoarthritis (wear-and-tear arthritis) of the knees is increased. Obese people have difficulty squatting (getting on and off the toilet, getting out of a car), running and climbing stairs. Biomechanically this is explained because the force on one’s knees between the patella (kneecap) and its articulation with the rest of the knee is about three times your body weight with walking.
When these other activities are undertaken, the forces can reach six to 10 times body weight. That is, the force on a 200-pound person’s knees while walking, is 600 pounds, and when they are climbing, running, squatting, etc., the force approaches 1200-2000 pounds. Multiply that by the number of years a person is overweight and you get excessive wear, and thus arthritis.
The corollary is true as well, and this provides a nice incentive to lose weight. The bang for the buck for the knees is 3-10 pounds of wear reduction for every pound lost! That means that simply losing 10-20 pounds can make a real difference in one’s activity and comfort level. Moderate exercise and leg-strengthening exercises can reduce the effective joint forces as well.
Unfortunately, obesity accompanied by arthritis creates a vicious cycle of inactivity and pain that prevents exercise. Patients with arthritic joints have a tendency to be more sedentary, which leads to weight gain. The weight gain in turn can make exercise more difficult, so the patient becomes more sedentary, creating the full effect of a negative spiral.
Obesity also affects spinal mechanics. Truncal obesity with a panniculus (doctor-speak for a big gut) causes an anterior bending force and a compressive force on the spinal column, thus leading to disc pathology and back pain. Just imagine wearing a backpack backwards with 50-75 pounds in it for a day and you get the idea.
Hip and Knee Replacements
As an orthopedist specializing in hip and knee replacements, I often see obese patients with severe knee arthritis. In fact, this is a wide-scale, increasing problem. Some are too overweight to physically perform surgery on, notwithstanding the inherently higher perioperative risks that they have, including anesthetic difficulties, infections, blood clots, medical problems and poorer functional outcomes.
Surgery for overweight patients presents greater challenges from a technical, as well as a rehabilitation standpoint. Technically the surgery is much more difficult to perform and therefore the chance of intraoperative complication is markedly increased. Rehabilitation is also impaired because it is so difficult for these patients to mobilize following lower extremity surgery.
Joint replacement in and of itself, will not enable patients to lose weight. Patients claim they can’t lose weight because they can’t exercise, but several studies have shown that these patients do not lose weight following joint replacement. They don’t hurt, but they don’t lose weight either. Unfortunately, very few of us who set out to lose weight actually do so. It truly must be a change in lifestyle, not just relief of joint pain, which enables weight loss.
Research shows that overall, obese joint replacement patients do worse functionally than thinner patients. But, studies also show that obese joint recipients in the short term have equally high satisfaction scores with the procedures. It was initially felt that because of increased weight on artificial joints the implant would wear out sooner in the obese patient. This, however, is not necessarily the case because these people are not really as active as their normal weight counterparts.
In summary, obesity is bad for the musculoskeletal system. With the average lifespan increasing, it would be prudent to keep your weight at a reasonable level and to keep fit, so that you may better enjoy those extra years without the pain and limitations of musculoskeletal wear.