GLP-1s Before Knee or Hip Replacement: Average Loss Was 9 Pounds at Mayo, and the Outcome Studies Point Both Ways

Surgeons at the Mayo Clinic in Rochester, Minnesota, looked back at 6,482 hip and knee replacements done there between 2019 and February 2023. The share of patients taking a GLP-1 drug before surgery rose from 2% in 2019 to 5% in 2022. Their study, published in Arthroplasty Today in August 2026, then asked how much weight those patients lost before the operation.

The average was 9 pounds. The range ran from a loss of 110 pounds to a gain of 36, and 19% of GLP-1 users lost 20 pounds or more. Average BMI fell by 1.4 points. After adjusting for other factors, GLP-1 use was not linked to fewer revisions, reoperations, or complications.

That result sits awkwardly next to the 68-week STEP 9 trial described below, where people with knee osteoarthritis lost 13.7% of their weight on semaglutide 2.4 mg. The Mayo records cover 2019 to early 2023, the drugs and doses varied, and patients took them for different lengths of time before surgery, so the two numbers measure different things. The Mayo team called for more study of newer GLP-1 drugs before joint replacement. Most of the other studies here report what happened after surgery, not how much weight patients lost beforehand, even though that is the number a BMI cutoff depends on.

Many surgeons set a BMI limit for elective hip and knee replacement. In a 2024 survey of members of the American Association of Hip and Knee Surgeons, published in February 2026, 45% of 534 respondents said they used a BMI cutoff below 40 for hip replacement and 42% used the same cutoff for knees. About a quarter said they had no strict cutoff. Most, 68%, gave patients up to one to two years to bring their BMI down, and 28% of 210 respondents said their patients used weight-loss drugs such as GLP-1s.

The number 40 is a policy choice more than a biological line. In a Rothman Institute study of 18,173 hip and knee replacements, infection risk within 90 days rose gradually with BMI, and no cutoff predicted infection much better than chance. Patients with a BMI of 40 or more did have about three times the infection risk, which is why the authors said surgery for them needs careful weighing. A University of Iowa analysis of national data found that BMI cutoffs exclude women and Black patients from surgery at higher rates.

So a GLP-1 prescription can decide whether someone gets on the operating schedule at all. Whether it also changes what happens after surgery is a separate question, and the answers so far conflict.

Several large studies of insurance claims and health records have linked GLP-1 use before surgery with better short-term results. The Hospital for Special Surgery in New York looked at knee replacement patients with a BMI of 40 or higher. Those who took a GLP-1 for at least three months before and after the operation were compared with matched patients not on the drugs. The GLP-1 group had fewer joint infections within 90 days (1.0% vs 1.8%) and fewer readmissions (5.3% vs 8.9%). Their complication rates were close to those of patients with a BMI of 35 to 39.9.

Johns Hopkins researchers, using the TriNetX health-records network, reported a 42% lower risk of joint infection after hip replacement among GLP-1 users and a 47% lower risk of readmission after knee replacement. The newest study came out in October 2026 in The Journal of Knee Surgery. A University of Arizona College of Medicine-Phoenix team compared 11,765 matched pairs of knee replacement patients. GLP-1 users had fewer heart attacks afterward (25 vs 47; risk ratio 0.53), fewer deep vein clots (risk ratio 0.72), and fewer blood clots overall (0.77). Clots in the lungs did not differ significantly.

The table's fourth row comes from the same TriNetX network as the Arizona knee study. A University of Texas Medical Branch team matched 1,259 shoulder replacement patients on GLP-1 drugs with 1,259 who were not. The GLP-1 group had higher rates of deep vein clots (1.6% vs 0.9%), heart attacks (1.6% vs 0.9%), pneumonia (3.34% vs 1.50%), transfusion, and readmission within 90 days.

Shoulder and knee surgery differ, so the two studies can both be right. But the pair shows how much these results depend on who ends up taking the drug. Records studies match patients on recorded age, sex, diabetes, and other diagnoses. They cannot match on things the records don't capture well, such as how closely a doctor follows the patient, whether the patient can afford the drug, or why it was prescribed.

A systematic review in The Journal of Bone and Joint Surgery, published in April 2026, pooled eight such studies covering 22,611 GLP-1 users and 77,810 controls. Readmissions fell in three studies, by 29% to 47%. Joint infections fell in five studies and showed no difference in three. Some studies found more blood vessel and lung problems among GLP-1 users. At two years, the reviewers found no consistent advantage. None of the eight was a randomized trial.

Two October 2026 studies compared the two most-used drugs directly, again with TriNetX records. A Cleveland Clinic team matched 2,858 hip or knee replacement patients on tirzepatide (Zepbound, Mounjaro) with 2,858 on semaglutide (Wegovy, Ozempic). At 90 days and one year, no surgical, medical, or implant outcome differed. At two years, tirzepatide users had lower odds of mechanical problems with the implant and of joint infection (odds ratio 0.64 for each), while reoperation rates did not differ significantly. The authors called the findings preliminary.

A University of Pennsylvania study of rotator cuff repair in adults aged 40 to 80 found that tirzepatide users needed a repeat repair less often within two years (2.83% vs 5.67%). Users of either drug had about 16% fewer complete re-tears than matched patients on neither. The authors noted that their outcomes came from billing codes and health care use, not imaging that confirmed the tendon had healed.

For knee osteoarthritis itself, the evidence is stronger, because it comes from a randomized trial. In STEP 9, published in The New England Journal of Medicine in 2024, 407 adults with obesity and moderate knee osteoarthritis took semaglutide 2.4 mg or placebo for 68 weeks. Knee pain scores on a 0-to-100 scale fell 41.7 points on the drug and 27.5 on placebo, and weight fell 13.7% versus 3.2%. Our arthritis guide covers that trial and Lilly's investigational retatrutide trials in more detail.

Whether that relief delays surgery is less clear. A Case Western Reserve University study of TriNetX records from 2021 to 2023 found that among adults with obesity and existing hip or knee osteoarthritis, GLP-1 users were less likely to have a hip replacement within a year (1.1% vs 2.2%) or a knee replacement (1.4% vs 2.1%). The same study found that among people without osteoarthritis, GLP-1 users were slightly more likely to be diagnosed with it, a pattern the authors said needs further study.

Every one of these studies sits beside a separate rule: anesthesia teams want to know when you took your last dose, because GLP-1 drugs slow stomach emptying and raise the worry of food in the stomach during anesthesia. Hold times differ by drug, dose, and hospital. Our guide to GLP-1s and anesthesia covers the current guidance, including a 2025 orthopedic study that recommended a 14-day pause before joint replacement.

The first randomized trial of a GLP-1 before knee replacement shows how researchers are handling this. A University of Hong Kong team published its protocol in Bone & Joint Open in July 2026. It plans to randomize 54 adults aged 40 to 80 with a BMI of 27 or higher who are on the list for knee replacement, giving half of them semaglutide for 48 weeks before and 48 weeks after surgery, with a four-week break on each side of the operation. Its main goals are feasibility and tolerability, so it will not settle whether the drug improves surgical results.

If a GLP-1 is part of your plan to qualify for a joint replacement, these questions can help:

• What BMI does this surgeon or hospital require, and is it a firm cutoff or a target?
• How long will they wait while you lose weight, and how will they check progress?
• How long before surgery should you stop the drug, and when can you restart?
• If you take it for diabetes, what will replace it for blood sugar control while you pause?
• How will you keep up protein and strength during weight loss, since muscle matters for rehabilitation? Our guide to protein and resistance training on GLP-1s covers the basics.

GLP-1 drugs are one way patients try to reach a surgeon's weight target, though at Mayo the average loss before surgery was modest. Some records studies find fewer infections and readmissions afterward and others don't. None yet shows that the drugs make a joint replacement last longer, and the one randomized trial under way is small.