Obesity is a risk factor for osteoarthritis of the hip and knee. People with obesity are at a 2-3 times higher risk of complications after joint replacement surgery, such as infection, joint loosening, and mechanical joint failure, any of which can lead to the need for a revisional surgery. Weight loss is encouraged before joint surgery to reduce these risks. For a person living with obesity who has had already had a hip or knee replaced, can weight loss with obesity medication reduce the risk of needing a revisional surgery?

A new study , published in JAMA Open, performed a retrospective cohort target trial emulation analysis using a UK database to address this question. They evaluated the association of weight loss within 1 year of starting weight loss medication, with the 5-year and 10-year risk of having a revisional joint surgery, amongst people who had had knee or hip replacement between 2000-2023.

They found that amongst 3691 qualified participants, the 5 year risk of needing a hip or knee revisional surgery was:

  • 5.6% for those who had stable weight or weight gain within 1 year of starting weight management medication
  • 4.4% for those who lost 2-10% weight within 1 year of starting weight management medication
  • 3.7% for those who lost 10% weight or more within 1 year of starting weight management medication

Said another way, people who lost 10% weight or more had a 43% lower risk of needing revision surgery, and those who lost 2-10% weight had a 25% lower risk of needing revision surgery, compared to those who had stable weight or weight gain. Results were similar for hip vs knee replacement, and 10 year results were similar to 5 year results.

While the design of this study has many limitations, cost, duration, logistical and ethical concerns of doing a rigorous (eg randomized controlled) trial to answer this question would be prohibitive. Weight loss medications that people in this study were taking included orlistat, sibutramine (since withdrawn from the market) , GLP1 receptor agonists, and
rimonabant (since withdrawn from the market); it would be interesting to see data with a focus on currently available and especially the highly effective newer weight loss medications. This study only evaluated weight loss within 1 year of starting weight management medication; I would also like to see what the impact of longer term sustained weight loss may be on joint replacement survivorship.

BOTTOM LINE: This study suggests that successful weight loss with weight management medication can reduce the risk of needing revisional joint surgery after hip or knee replacement. While it’s preferable to optimize weight before joint replacement, if you’ve had hip or knee replacement in the past, starting a new weight loss journey now may have benefits to preseve that precious joint!

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