Obesity is straining America's knees

America's expanding waistline is straining its knees--and pocketbook--with hundreds of thousands of overweight people undergoing surgery every year because the extra pounds they pack are leading to tears in their meniscal cartilage.

In the first major study of its kind, University of Utah School of Medicine researchers found the likelihood of tearing the meniscus, the cartilage that bears much of the load on the knee joint, increases dramatically with body mass index (BMI). (BMI is a measure of body fat based on height and weight. People with a BMI greater than 25 are considered overweight, and those with a BMI of more than 30 are considered obese.)

Overweight people are at least three times more likely to tear their meniscus, while the most obese men and women are 15 and 25 times, respectively, more likely to tear the cartilage, the U researchers report in the May edition of the American Journal of Preventive Medicine.

All the extra weight Americans are lugging around accounts for up to 450,000 out of 850,000 operations for meniscus tears annually, the researchers conclude. At an average of $3,000 per operation, that adds a whopper of a bill to the nation's medical costs, according to Kurt T. Hegmann, M.D., M.P.H., research associate professor of family and preventive medicine, who led the study.

"There's a potential savings of $1.3 billion in the costs associated with meniscus tears in overweight and obese people," said Hegmann, director of the U's Rocky Mountain Center for Occupational and Environmental Health.

Hegmann and his U colleagues studied 515 patients who underwent meniscal surgery between 1996-2000 at LDS Hospital in Salt Lake City and Utah Valley Regional Medical Center in Provo, Utah. These patients were compared to a control group of 9,944 other Utahns enrolled in the National Cancer Institute's Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial during the same years.

Participants were grouped into 10 BMI categories, ranging from 20 to greater than 40. The study participants also were grouped in three age categories--50-59; 60-69; and 70-79.

The researchers calculated the Mantel-Haenszel ratio--an age-adjusted odds ratio--for the likelihood of meniscal surgery and found that men with a BMI of 27.5 and higher and women with a BMI of 25 or higher were three times more likely to tear their meniscus. Men whose BMI exceeded 40 were found to be 15 times more likely to tear their meniscus; women in that BMI category were 25 times more likely to tear the meniscus.

"Since 57.4 percent (164 million people) of the U.S. adult population is either overweight or obese, this relationship has potentially large implications for meniscal surgeries," Hegmann and his colleagues state in the article.

The prescription to correct the problem is not complex.

"…A population-based weight management program could decrease future burden on orthopedic and medical-care systems due to meniscal surgeries and treatment of other obesity-related conditions," the researchers state.