20% of patients demonstrate decrease in body weight, BMI after knee or hip replacement

A Mount Sinai School of Medicine study has found that patients often exhibit a significant decrease in weight and body mass index (BMI) after undergoing knee or hip replacement surgery (arthroplasty). The study is the first of its type to correct for the annual increase in BMI typically found in North Americans between the ages of 29 to 73 years. The study was recently published in Orthopedics.

A total of 196 Mount Sinai patients who had knee or hip replacement from 2005 - 2007 to treat osteoarthritis were randomly selected for the study. Mean patient age at surgery was 67.56 years, with about 65 percent female and 35 percent male. Of this group, 19.9 percent demonstrated a clinically significant decrease in weight (defined as the loss of five percent or more of body weight) and BMI following knee or hip replacement. In addition, the mean weight of the group dropped from 79.59 kg (175.47 lbs) to 78.13 kg (172.24 lbs) after surgery.

Significant BMI decrease was found to be greater in knee replacement patients (21.5 percent) than hip replacement patients (16.9 percent). Patients who were obese prior to surgery, with BMI greater than 30, were the most likely to experience significant post-surgery weight reductions.

"Total joint arthroplasties are performed with the intent of relieving a patient's pain and disability," said the study's lead author Michael Bronson, MD, Chief of Joint Replacement Surgery at Mount Sinai School of Medicine. "Both total knee patients and total hip patients experienced a statistically significant and clinically significant corrected weight loss following surgery, which indicates a healthier overall lifestyle."

The incidence of overweight and obese adults has been steadily increasing over the past five decades in the U.S. Lifestyle modification, consisting of changes in patterns of dietary intake, exercise, and other behaviors, is considered the cornerstone of overweight and obesity management. Overweight patients often argue that their osteoarthritis limits their mobility and ability to exercise. Thus, patients may feel frustrated that they are unable to lose weight, and are often hopeful that losing weight would be easier postoperatively.

These results suggest that patients have improved weight parameters when compared to North American adults. Dr. Bronson and his joint replacement team at Mount Sinai believe that additional studies of total knee and total hip arthroplasty postoperative patients, which also incorporate nutritional guidance and long-term fitness goals, may show even more encouraging results.