Semaglutide can improve knee osteoarthritis pain in people with obesity. Whether GLP-1 medications also protect the joint independently of weight loss remains an open question.
The short answer: Semaglutide can improve knee osteoarthritis pain in people with obesity. Whether GLP-1 medications also protect the joint independently of weight loss remains an open question. Recent experiments make that possibility more credible, but human studies have not settled it.
Osteoarthritis affects the whole joint, including cartilage, bone, and the joint lining. Losing weight can help knee pain by reducing the load on the joint. It may also change metabolic factors associated with osteoarthritis. Researchers are now asking whether GLP-1 medications do something additional inside the joint.
What has been shown in people?
The strongest trial is STEP 9, published in The New England Journal of Medicine in 2024. Researchers assigned 407 adults with obesity and painful knee osteoarthritis to semaglutide or placebo, alongside advice about diet and physical activity. After 68 weeks, the semaglutide group had lost an average of 13.7% of body weight, versus 3.2% with placebo. On a 100-point knee-pain scale, scores improved by 41.7 points with semaglutide versus 27.5 points with placebo.
That is meaningful evidence for pain relief. It does not tell us how much of the improvement came from the medication itself and how much came from weight loss. STEP 9 also did not establish that semaglutide repaired cartilage.
Another randomized trial gives an important counterpoint. In a 2021 liraglutide study, participants first followed an eight-week diet program. The 156 people assigned to treatment had already lost an average of 12.5 kg and reported less knee pain during that diet phase. Over the following year, those assigned to liraglutide lost about 3.9 kg more than those assigned to placebo, but had no additional improvement in knee pain. The comparison starts after substantial weight loss; it does not prove that weight loss cannot help pain, or that semaglutide lacks a direct effect. It shows that greater drug-associated weight loss does not guarantee additional pain relief in every setting.
What about cartilage and knee replacement?
In the Shanghai Osteoarthritis Cohort, people with type 2 diabetes and knee osteoarthritis who used GLP-1 medications had less knee surgery and slower measured cartilage loss than nonusers. Knee surgery occurred in 1.7% of 233 users and 5.9% of 1,574 nonusers. The users also lost substantially more weight, with an adjusted difference of 7.29 kg. A statistical model attributed 32.1% of the association with surgery to weight reduction.
These are promising observations, but people were not randomly assigned to treatment. Differences in their health, care, and weight changes could affect the results. The portion of an association that a statistical model does not attribute to weight loss is not proof of a direct drug effect.
The newer 2026 Cell Metabolism study tested that question more directly in mice. When researchers controlled for differences in food intake and weight loss, semaglutide still reduced signs of joint damage and pain sensitivity. The paper also reported a randomized human pilot study with joint findings that support further research. That pilot does not establish lasting cartilage repair in people or confidently separate a clinical benefit from weight loss. A second 2026 experimental study found less joint damage and pain behavior in mice without a significant change in body weight.
What does this mean for you?
If you have obesity and knee osteoarthritis, semaglutide may help you lose weight and reduce knee pain. If you do not lose weight, we cannot yet predict that a GLP-1 medication will improve your arthritis. We also cannot promise that it will regrow cartilage or prevent knee replacement.
Joint care is bigger than a number on the scale. Track your pain, walking, stairs, and strength along with weight; our guide to weight-loss goals beyond the scale can help. If you are beginning exercise, discuss knee-friendly modifications with your clinician or physical therapist and see our two-day strength-training guide. For more on how nutrition and GLP-1 medications can fit into the same plan, read Low-Carb Nutrition and Diabetes Medications.
The next useful human study would compare people who achieve similar weight loss with and without a GLP-1 medication, then measure pain, function, and joint structure over time. Until then, a possible direct effect is an exciting research question, rather than an established treatment benefit.
