GLP-1 Microdosing Before Knee or Hip Replacement: BMI, Complication Rates, and What the Arthroplasty Studies Show

The conversation usually starts in a surgeon's office. The knee or hip is worn out, the X-ray settles it, and then the BMI comes up. Higher weight raises the chance of infection and repeat surgery, so patients are often asked to lose some first. That is where GLP-1 medicines, and questions about low-dose or microdose GLP-1 use before knee or hip replacement, now enter the picture.

This article goes through what the arthroplasty research actually measured: how BMI changes surgical risk, what happened to people on semaglutide and other GLP-1 drugs at the time of surgery, and what the perioperative guidance says about the weekly dose. The studies used prescribed doses, most often for type 2 diabetes. We point out each place where that limits what a microdose user can take from them.

Why does BMI matter before knee or hip replacement?

BMI matters because infection and revision risk climb with each obesity class. A meta-analysis by Chaudhry and colleagues (JBJS Reviews, 2019) pooled 37 studies of knee replacement. Compared with people at a normal BMI, the risk of any revision surgery was modestly higher at BMI 35 and above, about double at 40 and above, and close to five times higher at 50 and above.

The extra risk is mostly infection, not implant wear. Chaudhry and colleagues found septic revision rose with BMI, while aseptic revision did not differ between groups. A larger meta-analysis by Onggo and colleagues (ANZ Journal of Surgery, 2021), covering 3,106,381 knee replacements, found that people with a BMI of 40 or more had higher odds of superficial infection (OR 2.44) and readmission (OR 1.33) than people without obesity.

Function after surgery held up better than the complication numbers suggest. Chaudhry and colleagues found similar functional gains across obesity classes, with a single study hinting at slightly lower scores above BMI 50. For many people the replacement still works well. The question is how to bring the infection and revision risk down before the operation.

Does semaglutide lower complications after knee replacement?

Semaglutide users had fewer joint infections and readmissions after knee replacement in one large study, along with more of several medical complications. Magruder and colleagues (Journal of Arthroplasty, 2023) matched 7,051 semaglutide users with diabetes to 34,524 controls in a national claims database.

The trade-off is the part that rarely gets quoted. Semaglutide users had a lower rate of prosthetic joint infection (2.1% vs 3.0%) and readmission (7.0% vs 9.4%). They also had higher rates of acute kidney injury (4.9% vs 3.9%), pneumonia (2.8% vs 1.7%), heart attack (1.0% vs 0.7%) and low blood sugar events (1.9% vs 1.2%). A claims database cannot separate the drug from the reasons it was prescribed, and people with more advanced diabetes may have been more likely to be on it.

Later work from the same group by Xu and colleagues (Journal of Arthroplasty, 2026) split knee replacement patients by BMI. In people with a BMI of 30 to 39.9, semaglutide use was linked with lower odds of 90-day joint infection (OR 0.53), 90-day revision (OR 0.54) and pulmonary embolism (OR 0.39). At a BMI of 40 or more, the differences were narrower, limited to aseptic loosening and heart attack.

Do GLP-1 drugs help more with hip replacement?

The hip data look stronger so far. In a second claims study, Magruder and colleagues (Journal of Arthroplasty, 2024) compared 1,653 semaglutide users with diabetes to 7,812 controls having a hip replacement. Readmissions and joint infections were lower, and medical complications, hospital stay and costs did not differ.

The best summary is a meta-analysis by Rudran and colleagues at Oxford (Bone & Joint Journal, 2026). It pooled ten matched cohort studies with 96,356 patients: 30,350 hip replacements and 66,606 knee replacements. Across both, GLP-1 use was associated with fewer 90-day surgical complications, medical complications and readmissions.

Split by joint, the hip group showed lower surgical complications (RR 0.63), medical complications (RR 0.55) and readmissions (RR 0.82). The knee group showed only lower readmission (RR 0.77). Two-year revision rates ranged from 1.7% to 3.3% in GLP-1 users and from 1.7% to 4.5% in controls. The authors rated the evidence very low certainty, and two of the ten studies had a serious risk of bias.

How much weight do people actually lose on a GLP-1 before surgery?

In routine practice, people lose less weight before joint replacement than most expect. Seward and colleagues at Mayo Clinic (Arthroplasty Today, 2026) reviewed 6,482 primary hip and knee replacements. GLP-1 use before surgery rose from 2% in 2019 to 5% in 2022. The mean weight change on a GLP-1 before the operation was 9 pounds, and BMI fell by a mean of 1.4 points.

The Mayo results also cut against the claims database studies. After adjusting for other factors, GLP-1 use was not associated with revisions, reoperations or complications over a mean follow-up of 3 years. A single-center study with detailed charts is a different kind of evidence from a national billing database, and the disagreement is a reason to treat the benefit as unproven.

Timing is the other open question. Seddio and colleagues at Yale (Journal of Arthroplasty, 2025) grouped people with type 2 diabetes by how long they had taken semaglutide before knee replacement. Lower odds of severe adverse events appeared after a minimum of two to three months of exposure (OR 0.25). The authors call this observational and say it cannot establish causation.

Can a GLP-1 ease knee pain or delay surgery?

At full dose, semaglutide reduced knee osteoarthritis pain in a randomized trial. STEP 9, reported by Bliddal and colleagues (New England Journal of Medicine, 2024), gave 407 adults with obesity and knee osteoarthritis semaglutide 2.4 mg weekly or placebo for 68 weeks, alongside diet and activity counseling.

Pain on the WOMAC scale fell by 41.7 points with semaglutide and 27.5 points with placebo, from a mean baseline of 70.9. Weight fell 13.7% versus 3.2%. Adverse events led 6.7% of the semaglutide group to stop treatment, compared with 3.0% on placebo, mostly for stomach and bowel symptoms. Our guide to GLP-1 microdosing and joint health covers the osteoarthritis research in more depth.

Whether the drugs delay surgery is less certain. Carter and colleagues (Regional Anesthesia & Pain Medicine, 2026) used the TriNetX records network to compare adults with knee osteoarthritis who did and did not take a GLP-1. Users had lower 8-year rates of knee replacement, and the gap grew with longer use of newer drugs.

Fewer replacements could mean slower joint damage, less pain, or simply fewer people pursuing surgery. A records study cannot tell those apart. The authors themselves say prospective trials are needed.

Should you stop a GLP-1 microdose before joint replacement surgery?

Not automatically. Guidance from five societies, including the American Society of Anesthesiologists, published by Kindel and colleagues (Surgical Endoscopy, 2025), says GLP-1 therapy may be continued before surgery in patients without an elevated risk of delayed stomach emptying and aspiration. The concern is food left in the stomach under anesthesia.

The guidance names the escalation phase and higher doses as factors that raise that risk. When there is concern, it suggests a liquid diet for at least 24 hours before the procedure, as is done before colonoscopy and bariatric surgery. A person holding steady on a low dose sits at the lower end of those risk factors, though the guidance does not address microdosing specifically. Our article on GLP-1 microdosing before surgery and anesthesia walks through the fasting rules.

Practical points to bring to the pre-op appointment:

• •The drug, the exact weekly dose, and the date of your last dose change
• •Any nausea, early fullness, reflux or vomiting in the past few weeks
• •Whether you have type 2 diabetes and take other glucose-lowering medicines
• •Your recent weight trend and how much protein you are eating, since recovery depends on muscle

Muscle is worth a moment of attention. Rehabilitation after a new knee or hip relies on the thigh and hip muscles, and weight loss can take some lean mass with it. Our guide to muscle preservation on a microdose covers protein and resistance training.

Frequently asked questions

Clinical references

1. Rudran B, Little CDJ, Palmer AJR, et al. Glucagon-like peptide-1 receptor agonists are associated with improved 90-day outcomes after total hip and knee arthroplasty: a systematic review and meta-analysis. Bone & Joint Journal. 2026. doi:10.1302/0301-620X.108B8.BJJ-2025-1486.R2
2. Magruder ML, Yao VJH, Rodriguez AN, et al. Does Semaglutide Use Decrease Complications and Costs Following Total Knee Arthroplasty? Journal of Arthroplasty. 2023. doi:10.1016/j.arth.2023.05.071
3. Magruder ML, Miskiewicz MJ, Rodriguez AN, Mont MA. Semaglutide Use Prior to Total Hip Arthroplasty Results in Fewer Postoperative Prosthetic Joint Infections and Readmissions. Journal of Arthroplasty. 2024. doi:10.1016/j.arth.2023.12.023
4. Xu JJ, Johnson MC, Lama G, et al. The Effect of Body Mass Index on the Efficacy of Semaglutide Use at the Time of Total Knee Arthroplasty. Journal of Arthroplasty. 2026. doi:10.1016/j.arth.2025.09.056
5. Seddio AE, Vasudevan RS, Gouzoulis MJ, et al. As Few as Three Months of Preoperative Semaglutide Exposure Prior to Total Knee Arthroplasty Is Associated With Reduced Postoperative Adverse Events in Patients Who Have Type II Diabetes. Journal of Arthroplasty. 2025. doi:10.1016/j.arth.2025.08.003
6. Seward MW, Cleary EJ, DeNovio AC, et al. Preoperative Weight Loss Before Total Joint Arthroplasty Using Novel Glucagon-Like Peptide-1 Agonists. Arthroplasty Today. 2026. doi:10.1016/j.artd.2026.102134
7. Carter V, Desverreaux E, Amin I, et al. Glucagon-like peptide 1 receptor agonist use and risk of arthroplasty for knee osteoarthritis: retrospective database analysis. Regional Anesthesia & Pain Medicine. 2026. doi:10.1136/rapm-2026-107658
8. Bliddal H, Bays H, Czernichow S, et al. Once-Weekly Semaglutide in Persons with Obesity and Knee Osteoarthritis (STEP 9). New England Journal of Medicine. 2024. doi:10.1056/NEJMoa2403664
9. Chaudhry H, Ponnusamy K, Somerville L, et al. Revision Rates and Functional Outcomes Among Severely, Morbidly, and Super-Obese Patients Following Primary Total Knee Arthroplasty: A Systematic Review and Meta-Analysis. JBJS Reviews. 2019. doi:10.2106/JBJS.RVW.18.00184
10. Onggo JR, Ang JJM, Onggo JD, et al. Greater risk of all-cause revisions and complications for obese patients in 3 106 381 total knee arthroplasties: a meta-analysis and systematic review. ANZ Journal of Surgery. 2021. doi:10.1111/ans.17138
11. Kindel TL, Wang AY, Wadhwa A, et al. Multi-society clinical practice guidance for the safe use of glucagon-like peptide-1 receptor agonists in the perioperative period. Surgical Endoscopy. 2025. doi:10.1007/s00464-024-11263-2