Knee and Hip Replacement Patients Getting Younger

Obesity may be driving increasing need for knee and hip replacements in steadily younger patients

/ Author:  / Reviewed by: Robert Carlson, M.D Beth Bolt, RPh

(RxWiki News) The impact of being overweight has far reaching health implications — implications that may be taking a toll at an earlier age.

In a new study, researchers found that packing on the pounds may be setting the stage for total knee or hip replacement at increasingly younger ages.

Further, the scientists found that being overweight or obese had a greater impact on the knee than the hip.

"Talk to your doctor about managing weight and impact on knees and hips."

Peter Derman, MD, MBA, of the Department of Orthopaedics at the Hospital for Special Surgery in New York City, led this research.

The goal was to understand why the increase in number of total knee replacements has outpaced the number of total hip replacements in the last two decades.

According to the research, in 1993, surgeons performed 1.16 total knee replacements for every total hip replacement. By 2009, that ratio had grown to 1.6 total knee replacements for every total hip replacement.

The researchers started by compiling data from the Nationwide Inpatient Sample on number of replacements, length of patient hospital stay associated with the procedure and in-hospital death associated with the replacements.

The team also looked at trends in body mass index (BMI), a common measure of obesity based on height and weight, obtained from the Behavioral Risk Factor Surveillance Services.

Dr. Derman and his colleagues found that BMI was the most important factor behind the increase in the number of knee replacements. These researchers also found that an increasing number of younger individuals were going through the operation.

Furthermore, the number of total knee replacements in patients considered overweight and obese far outpaced the same measure of total hip replacements.

People who are overweight typically fall in the BMI range of 25 or more. Obese is typically considered a BMI of 30 or more.

People between the ages 18 and 64 experienced a more rapid rise in overweight and obesity than people over age 65.

Between 1997 and 2009, there was a 56 percent increase in patients between the ages of 18 and 64 undergoing total knee replacement. The same age group had a 35 percent increase in total hip replacements.

“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," Dr. Derman said in a prepared statement.

"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," Dr. Derman said.

"If rates of overweight and obesity continue to climb, we should expect further acceleration in the number of knee replacements performed annually in the US with a more modest increase in hip replacement volumes," he said.

The research team concluded that to deal with the expected increase, there should be strategic decisions made to providing funding, surgical workforce and training.

Dr. Derman also noted that obesity prevention could potentially reduce the need for knee and hip replacements.

This research was published in the June edition of the Journal of Bone and Joint Surgery.

The authors did not disclose any conflicts of interest, financial or otherwise.

Review Date: 
June 6, 2014
Last Updated:
June 11, 2014