GLP-1 Medications and Knee Osteoarthritis Pain

If your knees complain on the stairs, you know how much they shape a day. Researchers have been curious about whether the weight loss from a GLP-1 medication also eases knee osteoarthritis pain, and a 2024 trial gives an encouraging first answer. Here is what it found, how to read it, and what it does not tell us yet.

Why knees and weight go together

Your knees carry your body weight with every step, so extra weight tends to add load, and osteoarthritis (the wear-and-tear kind of arthritis) is more common in people who live with obesity. That is why doctors so often suggest movement and weight management as part of knee care. The new question was whether a medication that produces large weight loss could help in a measurable way.

The STEP 9 trial

• Who took part: 407 adults with obesity and painful knee osteoarthritis. Most were women (about 82 percent), with an average age of 56 and an average BMI of about 40.
• What they received: once-weekly semaglutide or a placebo for 68 weeks, alongside advice on diet and physical activity for everyone.
• What was measured: body weight, plus knee pain and function on the WOMAC scale, a standard questionnaire scored from 0 to 100 where lower pain scores are better.

What the trial found

People taking semaglutide lost about 13.7 percent of their body weight, compared with about 3.2 percent in the placebo group. Pain scores came down in both groups, which is worth celebrating on its own: on average WOMAC pain fell by about 41.7 points with semaglutide and about 27.5 points with placebo, so the medication group improved by more. Physical function scores improved more with semaglutide as well.

Those figures come from published reports of the trial rather than the full paper, so treat the exact numbers as approximate and check the original if you plan to quote them.

A few kind reality checks

• The placebo group got better too. Advice on activity and diet, plus the attention of being in a trial, helped a lot of people feel better. That is a hopeful reminder that everyday habits matter for knees.
• Side effects were more common with the medication. About 6.7 percent of people in the semaglutide group stopped because of side effects, versus about 3 percent with placebo, mostly stomach-related. Our guide to side effects in the big GLP-1 trials goes through what people reported.
• It is not an approved treatment for osteoarthritis. The trial tested knee pain in people who were also living with obesity, so it says nothing about people with other body sizes or other joints.
• It was one trial of about a year and a half. We do not yet know how long the benefit lasts or how it compares with other knee care.

Looking after your knees, with or without a medication

Whatever your treatment plan looks like, these are well-worn, friendly steps to talk through with your care team:

• Keep moving gently. Walking is kind to most knees; see how much walking is enough for a starting point.
• Strengthen the muscles around the joint. Our strength training for beginners guide shows a simple place to begin, and everyday movement adds up too.
• Protect your muscle while weight comes down. Our look at muscle on GLP-1 medications explains why this matters.
• Ask about pain. A clinician or physical therapist can tailor exercises to your knees and check whether anything else is going on.

The takeaway for you

In this trial, large weight loss with semaglutide went hand in hand with bigger improvements in knee pain and function than placebo plus lifestyle advice alone. That is a promising sign, not a prescription. If knee pain is holding you back, a conversation with your doctor about all your options, including strengthening and weight management, is a great next step. If you are curious who these medications are labeled for, our guide to who qualifies for a GLP-1 medication is a good companion read.

Sources

• Bliddal H, et al. Once-weekly semaglutide in persons with obesity and knee osteoarthritis (STEP 9). New England Journal of Medicine, 2024 (design and results as reported by RxFiles, Medical Republic, HCPLive and MDedge; the full paper was not read).
• Arthritis Foundation and U.S. Centers for Disease Control and Prevention. General information on osteoarthritis, activity and weight.