An increase in the number of total knee replacement surgeries have been linked to obesity.

Researchers found that in increase in the prevalence of overweight and obese people in the United States accounted for 95 percent of the higher demand for knee replacements, with younger patients affected to a greater degree.

"We observed that growth of knee replacement volumes was far outpacing that of hip replacements and were curious as to the origins of this trend," Peter B. Derman, lead study author and an orthopaedic surgery resident at the Hospital for Special Surgery in New York, N.Y., said in a statement.

For the study, researchers reviews at least 10 years of national data (through 2009) on total knee replacement and total hip replacement, length of hospital stay, in-hospital mortality, and orthopedic workforce trends.

They found that patients ages 18 to 64 experienced a more rapid rise in overweight and obesity, compared to patients older than age 65. From 1997 to 2009, the share of patients ages 18 to 64 undergoing knee replacement rose 56 percent, compared with only 35 percent for hip replacement.

"We found that this differential growth rate in total knee replacement procedures could not be attributed to changes in physician or hospital payments, length of hospital stays, in-hospital death rates, or surgical work force characteristics," Derman said. "Because excess body weight appears to be more damaging to the knee than to the hip, the increasing prevalence of overweight and obesity may explain the growing demand for knee replacements over hip replacements."

Derman said if rates of overweight and obesity continue to climb, there may be further acceleration in the number of knee replacements performed annually in the United States with a more modest increase in hip replacement volumes.

"This knowledge can inform future policy decisions regarding health care funding and surgical workforce training as well as guide allocation of preventative health resources," he said.

The findings were recently published in the Journal of Bone and Joint Surgery.