Drop Some Pounds and Save Your Hips and Knees

Being overweight, particularly if you have a higher than average body mass index, may increase your risk for developing severe osteoarthritis in your hips and knees, according to research presented this week at the American College of Rheumatology Annual Scientific Meeting in San Francisco, Calif.

Osteoarthritis, or OA as it is commonly called, is the most common joint disease affecting middle-age and older people. It is characterized by progressive damage to the joint cartilage—the slippery material at the end of long bones—and causes changes in the structures around the joint. These changes can include fluid accumulation, bony overgrowth, and loosening and weakness of muscles and tendons, all of which may limit movement and cause pain and swelling.

Swedish researchers recently measured the body mass, waist, waist-to-hip ratio, weight and percentage of body fat of 11,026 male and 16,934 female members from the general population—who ranged in age from 45 to 73 years—and of that group, 1,022 OA patients who had undergone joint replacement surgery were identified 11 years later.

Researchers then compared 471 patients who had total knee replacement and 551 patients who had total hip replacement due to OA with those who did not to define the relationships between body mass and knee and hip OA leading to joint replacement. They also explored the relationships between C-reactive protein, metabolic syndrome and the incidence of severe knee and hip OA.

After adjusting for other important risk factors, including age, sex, smoking status, other illnesses, C-reactive protein, and physical activity level, researchers determined that being overweight by any measure identified was associated with knee OA leading to joint replacement. Of all measures, a higher body mass was the biggest risk factor associated with developing severe hip or knee OA for both men and women.

In this study, which is the largest and the first that compares the effect of different measures of body mass on the risk of severe OA over time in the knees and hips of both men and women in the same population, investigators also demonstrated that the risk increase of developing severe OA is more strongly related to increased joint loading due to being overweight than to the metabolic changes associated with being overweight or obese (such as, increased CRP and metabolic syndrome).

“[Being] overweight is one of the few factors leading to osteoarthritis that we can actually do something about,” explains Stefan Lohmander, MD, PhD; professor and senior consultant; Lund University, department of orthopaedics, clinical services, Lund, Sweden, and lead investigator in the study. “Understanding the connection between being overweight and getting osteoarthritis, and the size of the risk, is therefore important when considering disease prevention. We have shown that the risk increase starts already with being moderately overweight, and increases with each further increase in body mass. This is true for men and for women, and for knees and for hips.”