Extra body weight multiplies the load on your knees, and guidelines strongly recommend weight loss for knee osteoarthritis. In the STEP 9 trial, semaglutide plus counseling reduced knee pain scores more than counseling alone, though it is not approved for osteoarthritis.
Body weight and knee pain are closely connected. Each unit of weight you carry adds roughly four units of force across the knee with every step, so reducing weight is one of the most effective, guideline-backed ways to ease knee osteoarthritis. A 2024 trial found that semaglutide, added to diet and activity counseling, reduced knee pain scores more than counseling alone in people with obesity, though GLP-1 medications are not FDA-approved to treat osteoarthritis.
The CDC lists joint pain (especially with movement), stiffness after rest, swelling and reduced range of motion as typical symptoms of osteoarthritis. It names joint injury or overuse, older age and obesity as risk factors, noting that extra weight can also affect metabolism in ways that raise risk.
The mechanical effect is larger than most people expect. A 2005 study in Arthritis and Rheumatism measured walking forces in 142 older adults with overweight or obesity and knee osteoarthritis at the end of an 18-month diet and exercise trial, relating their knee loads to how much weight they had lost. Every kilogram of weight lost was associated with roughly a 4-kilogram drop in compressive force at the knee. The authors put it plainly: each pound of weight lost results in a 4-fold reduction in the load on the knee per step. Over thousands of steps a day, that adds up.
The 2019 guideline from the American College of Rheumatology and the Arthritis Foundation makes two strong recommendations relevant here:
The IDEA trial, published in JAMA in 2013, tested how weight loss and exercise interact. It enrolled 454 adults aged 55 and older with knee osteoarthritis and a BMI of 27 to 41, and assigned them to exercise only, diet only, or diet plus exercise for 18 months.
| Group | Average weight loss |
|---|---|
| Exercise only | 2.0 percent |
| Diet only | 9.5 percent |
| Diet plus exercise | 11.4 percent |
The diet-only group had lower knee compressive forces than the exercise-only group. The diet plus exercise group reported less pain and better function than both other groups, and better physical quality of life than the exercise group. The takeaway is that weight loss reduces joint load, while combining it with exercise gave the best results for how people felt and functioned.
STEP 9, published in the New England Journal of Medicine in 2024, is the main trial of a GLP-1 medication in knee osteoarthritis. It enrolled 407 adults with obesity (average BMI 40.3) and moderate knee osteoarthritis with at least moderate pain. The average age was 56, and 81.6 percent were women. Participants received semaglutide or placebo for 68 weeks, and everyone received counseling on physical activity and a reduced-calorie diet.
Results at 68 weeks, as averages:
Serious adverse events were similar between groups. Stopping treatment because of side effects was more common with semaglutide (6.7 percent) than placebo (3.0 percent), mostly due to gastrointestinal effects.
The Wegovy label lists weight management, cardiovascular risk reduction and a liver indication, but not osteoarthritis. A GLP-1 medication may be prescribed for weight management in someone who meets those criteria and also has knee pain, but prescribing it only to treat osteoarthritis would be off-label.
Compounded semaglutide and tirzepatide are not FDA-approved and were not studied in STEP 9. Dosing for any of these medications is set by the prescriber.
Whatever role medication plays, the guideline-recommended foundation stays the same: regular exercise that fits your body and preferences, plus weight reduction if you carry extra weight. Our strength training guide offers a low-barrier starting point, and keeping muscle during weight loss is covered in protein and muscle preservation.
The American College of Rheumatology guideline notes that losing 5 percent or more of body weight can be associated with meaningful changes, and that benefits continue to grow with larger amounts. In the IDEA trial, people who averaged about 11 percent weight loss with exercise reported the least pain.
No. STEP 9 showed reduced knee pain scores compared with placebo in people with obesity, but osteoarthritis is not an FDA-approved use. Semaglutide may be prescribed for weight management in people who meet label criteria, and a licensed provider can explain whether that applies to you.
Guidelines strongly recommend exercise for knee osteoarthritis, and the trials behind that recommendation included people with pain. There is no single pain level that rules exercise in or out, so it is worth deciding with your clinician when and how to start.
The studies here measured pain, function and joint load rather than changes in joint structure, so they cannot show reversal. Weight loss reduced the force on the knee and improved symptoms on average, which is valuable on its own.
If knee pain is limiting your activity, a licensed provider can help you sort out the cause, check whether weight is a contributing factor and talk through options that fit your health history. Persistent swelling, sudden severe pain or a joint that gives way also deserve prompt evaluation. This article is educational and does not determine eligibility for any treatment.
Written by the NewDay Wellness editorial team from the sources above and checked against them before publication, and medically reviewed by Dr. Sean Arora and Dr. Shannon Arora of Arora Health & Aesthetics; see our editorial standards. This article is educational and does not diagnose conditions, establish eligibility for any medication, or replace care from a licensed provider. Compounded medications are not FDA-approved.
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