For years, knee surgeons have been nudging patients toward pre-op weight loss with the promise that shedding pounds might smooth the road after total knee arthroplasty (TKA). But a new retrospective cohort study out of Mayo Clinic throws some cold saline on that assumption.
Published August 11, 2025, in The Journal of Bone and Joint Surgery, the study — led by Michael Seward, M.D., Jessica Grimm, M.S., Charles Hannon, M.D., M.B.A., Nicholas Bedard, M.D., Daniel Berry, M.D., and Matthew Abdel, M.D. — followed 3,665 patients with BMI ≥30 kg/m² who underwent primary TKA. Here’s the study: “Weight Loss Before Total Knee Arthroplasty Was Not Associated with Decreased Postoperative Risks.”
The verdict? Dropping weight before surgery didn’t translate into fewer complications. In fact, in some cases, it may have made things worse.
Who Did What on the Scale
Patients were grouped by weight change between 1 and 24 months pre-op.
- Weight gain ≥5 lbs: 20%
- Stable weight: 39%
- Lost 5–<10 lbs: 17%
- Lost 10–<20 lbs: 15%
- Lost ≥20 lbs: 9%
At first glance, some patterns emerged. Gaining >5 lbs? Higher odds of longer hospital stays and more complications. Losing 10–<20 lbs? Surprisingly, higher risks of revision, periprosthetic joint infection (PJI), and overall complications.
But here’s where it gets interesting: after multivariable adjustment, only two associations stuck.
- Losing 10–<20 lbs = 2.6x higher risk of PJI (p=0.01)
- Gaining >5 lbs = 50% higher complication risk (p=0.03)
So much for the “just lose a little weight and you’ll be fine” mantra.
Beyond the Scale
Obesity is still a well-known risk factor in arthroplasty, but this study suggests the story isn’t as simple as the number on the chart. Nutritional status, comorbidity control, and physical conditioning may all matter just as much — or more — than a pre-op diet push.
With an average follow-up of six years, the authors conclude that counseling should focus on comprehensive optimization, not just the scale.
The Take-Home for Knee Surgeons
If your patient is obese and headed for TKA, short-term weight loss alone may not be the magic bullet we once hoped. The knee still wants stability, nutrition still counts, and comorbidities still demand attention.
