Last reviewed: September 29, 2026

Usually you can. Being overweight is not on its own a reason to be turned down, but the risks rise with weight, most clearly at the highest weights.

People with obesity have more infections and wound problems after a knee replacement than people who are not obese, and more of their knees are redone, mostly because of infection. Risks are clearly higher at a body mass index of 40 or more.

Weight is not the whole story. Diabetes, which is more common in heavier people, raises the risk of infection on its own. But studies that took diabetes and overall health into account still found more infections at the highest weights. People with both severe obesity and diabetes had the most infections.

Some risks around the operation itself also rise at the highest weights. At a body mass index of 40 or more, a large US database found more breathing problems needing the breathing tube to be put back in, more blood clots in the lungs and more kidney problems in the month after surgery.

The improvement from surgery is about the same. People with obesity gain about as much pain relief and function as people who are not obese. The American Academy of Orthopaedic Surgeons guideline found no difference in function after surgery between people with a body mass index under 30 and those between 30 and 40.

Whether losing weight first helps is less clear than many people are told. In a large study from the Mayo Clinic, people with obesity who reached common weight-loss goals before surgery did not have fewer problems afterward. A pooled review found the same. In people with a body mass index of 40 or more, losing about 20 pounds was linked to a shorter hospital stay, but not to a better knee. These studies are records, not trials.

A guideline from rheumatologists and hip and knee surgeons says obesity alone should not delay a knee replacement once other treatments have stopped working. The evidence behind it is rated low.

In general:

  • Weight on its own does not rule out a knee replacement.
  • The higher the weight, the higher the risk of infection, which is worth discussing openly with your surgeon.
  • Tell your surgeon and anesthesiologist if you have sleep apnea or use a breathing machine at night.
  • Losing a modest amount of weight shortly before surgery has not been shown to lower the risks.
  • Sustained weight loss can ease arthritis pain, whether or not you have surgery.

Drafted with AI assistance from published sources, reviewed and edited by Babak Sheikh, MD.

Sources:

This is general information about what published research shows. It is not medical advice and it is not about your situation. Reading it does not create a doctor-patient relationship with me. I am a retired orthopedic surgeon and I do not see patients. Talk with your own doctor before changing anything about your care. If something feels suddenly or seriously wrong, get medical care promptly rather than waiting.

This page is provided as is. I make no guarantee that it is accurate, complete or current, and medical evidence changes. Use of it is at your own risk.

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