Older people get the blame but it is younger people whose rising rate of obesity is driving the increasing number of knee replacements in the U.S. That is the conclusion of a study that examined data from 9, 000 knee replacements gathered by more than 125 orthopedic surgeons from 22 states. The analysis revealed that 55% of patients younger than 65 were obese compared with 43% of those who were 65 or older.
Obesity in Young Driving TKA Rate

Compared with those 65 and older, twice as many of the patients younger than 65 were severely obese (5% versus 11 %, ). The researchers found that the younger group of patients also had higher rates of smoking and lower mental health scores.
“Our study shows that younger patients are more obese and experience the same amount of pain and functional disability as older patients and in some cases even more, ” study author David Ayers, M.D., director of the Musculoskeletal Centre of Excellence at the University of Massachusetts Medical School, said in a university news release.
“What we’re seeing is that the rise in obesity rates in younger people is having a dramatic influence on the number of total joint replacement surgeries, ” he said. Surgeons now perform about 600, 000 knee replacement surgeries a year. Ayers expects that number to grow to 3.48 million procedures a year by 2030.

Discussion
This is a fascinating development. In my practice we've seen similar outcomes with the revised protocol. The key differentiator seems to be patient selection criteria. Has anyone else noticed the correlation with BMI thresholds?
Great point. I'd push back slightly on the conclusion, the sample size in the cited study is too small to draw population-level inferences. That said, the directional signal is compelling and worth a larger RCT.
We implemented a similar approach last year. Early results are promising but we're still gathering 12-month follow-up data. Happy to share our protocol if anyone is interested.
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