Hip and knee replacements, also known as total joint arthroplasties (TJAs), are common surgical procedures that relieve pain and increase mobility and could potentially cause weight loss as a by-product.

Knee replacements have long been known to increase mobility in older patients, however, this new research touches on the whether hip and knee replacements actually have weight benefits.

About 700,000 TJAs are performed each year in the United States. Maria Inacio, a doctoral candidate from the San Diego State University/University of California, San Diego, and her team of colleagues proposed this question in a recent study that was published in Clinical Orthopaedics and Related Research, a journal by Springer.

Hip and knee replacement candidates usually have a high rate of obesity. After surgery, as mobility and activity increase, it is presumed that weight loss would occur. This weight loss would be beneficial in preventing further surgery by decreasing difficulties, such as prosthetic loosening.

The team of researchers reviewed 12 studies with the same criteria, but felt these studies presented bias because of small sample sizes and substandard methods. Conclusions showed that between 14 and 49 percent of patients had lost weight a year after having a TJA. Despite this, differences in study designs as well as variations in the amount of weight lost, implied there is no consistent or conclusive pattern.

Stuart B. Goodman, MD, PhD, of Stanford University said:

“Obese patients frequently tell clinicians that they are overweight because their painful hips or knees limit their physical activities and their capability to ‘burn calories.’ Unfortunately, after a comprehensive analysis of the data, the answer to this important question is still unknown.”

Inacio and her team believe further research in this field is required, including a large nationwide survey, because hip and knee replacements are so common. There is not enough compelling evidence today to provide exact insight into the outcomes of hip and knee replacements.

Written by Kelly Fitzgerald