Obesity tough on the knees, and men’s hips
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Obesity raises the risk of severe knee arthritis and may do similar damage in the hips, but perhaps only in men, a new study suggests.
Researchers found that among nearly 2,600 older Icelandic adults, those who were overweight were more likely to have had a total knee replacement due to severe arthritis. Obese men and women were particularly at risk.
When it came to the odds of total hip replacement, obese men were again at greater risk. However, weight was not a factor for women, the researchers report in the Annals of Rheumatic Diseases.
The findings underscore the importance of body weight in knee arthritis risk, according to lead researcher Dr. Jonas Franklin of Lund University in Sweden.
“There are by now several studies that show that being overweight is a risk factor for developing osteoarthritis of the knee,” he told Reuters Health. “Being obese means even greater risk.”
While normal-weight people do develop the condition as well, Franklin noted, it is “clearly advisable” for people to try to maintain a healthy weight as they age.
Hip arthritis, however, is a more complex question, according to Franklin. Studies have come to conflicting findings as to whether weight has an impact. And these latest findings, he said, appear to be the first to suggest that obesity is a stronger risk factor for hip replacement in men than in women.
The findings are based on 1,473 Icelandic adults who had undergone a total knee replacement or total hip replacement, plus 1,103 of their first-degree relatives who had not had either surgery. On average, participants in both groups were in their early 70s.
Overall, the researchers found, overweight women were 60 percent more likely than thinner women to have needed a knee replacement. Obese women, meanwhile, had a four-fold greater risk.
Similarly, overweight men had a 70 percent higher risk of knee replacement, while the odds were increased five-fold among obese men.
A different pattern emerged with hip replacement. Obesity raised men’s risk by 70 percent, while being overweight had no clear effect. Among women, there was no relationship between weight and hip replacement.
The reasons for the findings are unclear—though sex differences in the anatomy of the hip or other biological factors may play a role, the researchers speculate.
Franklin said that more studies are needed to confirm whether the sex difference is real or just a “statistical fluke.”
SOURCE: Annals of Rheumatic Diseases, online May 27, 2008.
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