Retatrutide knee osteoarthritis results showed less pain than placebo, a treatment without the active medicine. The largest reported pain drop came from the 9 mg group, not the highest dose. Lilly's November 5 announcement previews a conference presentation; it doesn't establish that a damaged knee has repaired itself or tell someone taking another medicine to switch.
Osteoarthritis is joint disease affecting cartilage, the smooth covering on bone ends, and surrounding tissues. The earlier semaglutide knee osteoarthritis study provides useful context for this new announcement.
Retatrutide knee osteoarthritis: what happened
As of November 5, 2026, the day this article was written, Lilly's announcement dated November 5 previews knee-pain results at ACR Convergence, the American College of Rheumatology's meeting. It runs November 6–11 in Orlando.
Lilly reports pain reductions “by up to an average of 4.5 points (75.8%) from an average baseline of 6.0”. That's on WOMAC, a questionnaire about arthritis pain, stiffness and everyday movement. This trial used a 0–10 pain scale, with higher scores meaning worse pain.
The 68-week TRIUMPH-4 study gets a November 8 presentation, Abstract #0871. An 80-week knee subgroup from TRIUMPH-1 gets a November 10 poster, Abstract #2573. These are late-stage, phase 3 studies. Today's release previews those presentations; it is not a full TRIUMPH-4 paper reviewed by outside experts.
What it means for someone already considering tirzepatide
The finding makes knee pain part of the weight-treatment conversation. It doesn't make retatrutide and tirzepatide interchangeable. Neither knee trial compared them directly.
Retatrutide activates three hormone receptors, the switches cells use to receive signals. Two are GIP and GLP-1, gut-hormone pathways involved in blood-sugar control; the third receives glucagon, a hormone involved in releasing stored fuel. Tirzepatide acts on the first two.
A person considering tirzepatide still needs a decision based on that medicine's evidence, health history and side effects. Retatrutide's separate Ozempic comparison answers a diabetes question, rather than this knee-pain question.
TRIUMPH-4 results: the dose and placebo matter
The headline isn't a new first result. Lilly's December 11, 2025 topline release, its initial summary, already reported these figures. TRIUMPH-4 enrolled 445 adults with overweight or obesity and knee osteoarthritis, without diabetes.
| Average change at 68 weeks | Retatrutide 9 mg | Retatrutide 12 mg | Placebo |
|---|---|---|---|
| Pain score, starting around 6.0 | −4.5 points | −4.4 points | −2.4 points |
| Body weight | −26.4% | −28.7% | −2.1% |
These are the release's efficacy-estimand figures: estimates assuming continued treatment without certain additional weight or pain treatments. The ACR abstract confirms the dose pattern. The largest pain drop came with 9 mg; the largest weight change came with 12 mg.
An analysis accounting for treatment stops reported smaller pain decreases: 4.0 points with 9 mg, 3.7 with 12 mg and 2.1 with placebo. Neither calculation predicts one person's result.
The 75.8% figure describes change from starting pain, not improvement beyond placebo. It was calculated after the original analysis plan. The pain-free finding was also an added analysis: 14.1% with 9 mg, 12.0% with 12 mg and 4.2% with placebo.
What the second knee study adds
Lilly's November 5 release also reports up to a 4.3-point pain decrease, or 73.1%, in TRIUMPH-1, with more than one in six retatrutide-treated participants pain-free. Again, the percentage change was calculated after the original plan.
The November 10 conference abstract identifies 12 mg as that 4.3-point group, versus 2.24 points with placebo. It covers 574 adults with knee osteoarthritis over 80 weeks.
As of November 5, 2026, the day this article was written, TRIUMPH-1 also has a New England Journal of Medicine paper, published online September 29. Its main knee analysis reported a 3.6-point decrease with 12 mg versus 1.9 with placebo. It handles treatment interruptions and other events differently. The conference figure and paper figure answer different statistical questions.
Where semaglutide fits
Semaglutide has its own knee trial, STEP 9, published in the New England Journal of Medicine in 2024. It enrolled 407 adults with obesity and knee osteoarthritis for 68 weeks and found greater average pain reduction than placebo.
That trial used a 0–100 pain scale. Its raw points cannot be placed beside TRIUMPH-4's 0–10 points as though the scales matched. Even converting scales wouldn't create a direct comparison between medicines.
For someone considering semaglutide, its own evidence remains relevant. Retatrutide's announcement supplies no estimate of what switching would do, and neither study establishes outcomes for compounded preparations prescribed through Promise.
Side effects belong beside the pain figures
Lilly's December release reported nausea, diarrhea, constipation, vomiting and reduced appetite. About four in ten retatrutide participants reported nausea: 38.1% with 9 mg and 43.2% with 12 mg, versus 10.7% with placebo.
Dysesthesia, an unpleasant abnormal skin sensation, occurred in 8.8%, 20.9% and 0.7%, respectively. Lilly described these dysesthesia events as generally mild and rarely leading to treatment stops.
Still, reported health problems led 12.2% of the 9 mg group and 18.2% of the 12 mg group to stop treatment, versus 4.0% with placebo. Lilly said these stops included perceived excessive weight loss. That matters alongside a headline about less pain.
What the news doesn't establish
A lower pain score doesn't demonstrate that cartilage grew back. These findings also don't separate the effect of losing weight from a direct effect on the joint. They concern selected adults with weight-related disease, rather than everyone with knee pain.
The separate retatrutide sleep apnea trials measure breathing interruptions during sleep. Their findings don't strengthen a cartilage-repair claim either. Different symptoms need their own measurements.
What a prescription conversation covers today
As of November 5, 2026, the day this article was written, FDA's page, marked current October 1, 2026, says retatrutide “cannot be used in compounding under federal law”. Lilly's November 5 release describes retatrutide as “an investigational molecule that cannot be legally sold or marketed for human use”; investigational means it is still being tested.
Tirzepatide and semaglutide prescribed through Promise are dispensed by a licensed U.S. compounding pharmacy as compounded medications, preparations made for individual prescriptions. These are different from FDA-approved products: the formulations offered here are not FDA-approved. A licensed provider may still prescribe — that decision is between you and your doctor.
The review considers weight goals, the knee diagnosis, existing medicines and manageable side effects. The prescriber sets any actual dose. At Promise, a licensed provider reviews every request, and not everyone qualifies.
What to watch after November 8
The November 8 presentation should provide more discussion of TRIUMPH-4's methods and safety findings; the November 10 poster covers the second knee group. A full peer-reviewed TRIUMPH-4 report remains an important next step.
This is worth revisiting after those presentations. The useful questions are concrete: how many people stayed on treatment, how missing pain scores were handled, and whether improvements lasted. For someone discussing treatment now, walking, stairs, pain and manageable side effects all matter alongside the number on a scale.
