Research has found that morbidly obese patients who dropped 20 pounds before their knee replacement surgery reduced their post-operative hospital stay by 1 day and were 76% less likely to stay longer than planned. Those with morbid obesity who only lost 5 to 10 pounds, however, did not experience the same benefit as per David S. Jevsevar, MD, MBA, of Dartmouth-Hitchcock Medical Center in Lebanon, New Hampshire. Jevsevar and colleagues’ work was published in the Journal of Bone and Joint Surgery.

“Losing at least 20 pounds was associated with lower absolute length of stay, lower odds of extended length of stay, and lower odds of being discharged to a facility,” the authors explained.

Analyzing data from 203 total knee arthroplasty patients, the researchers found that prior to the operation, 41% lost at least 5 pounds, 29% lost at least 10, and 14% lost 20 or more pounds. In addition to spending about one less day in the hospital, those who lost 20 pounds were also found to be 76% less likely to have a hospital stay of 4 or more days. These patients also saw a 72% decrease in their risk of being discharged from the hospital to another facility.

No improvements in outcome following the joint replacement surgery were seen in those who only lost 5 to 10 pounds, and a significant increase in the length of hospital stay and operation time was observed in those who gained weight prior to the procedure.

The patients in this study were all morbidly obese and had undergone a total knee arthroplasty between 2011 and 2016. These 203 patients accounted for 13.5% of the 1,500 patients who had received this joint replacement in that time.

Furthermore, there was no association between the loss of weight before the operation and a difference in time of operation or postoperative health gains. Jevsevar claimed that larger studies must be conducted to confirm any correlation between preoperative weight loss and improved outcomes after a knee replacement.

He did note that this research indicates that it may be wise for physicians to promote larger and more specific quantities of weight loss in their morbidly obese patients who are preparing to receive a knee replacement.