Experimental Weight-Loss Drug Eased Knee Pain Among Arthritis Sufferers, Clinical Trials Show

Key TakeawaysAn experimental weight-loss drug can help with knee arthritisRetatrutide caused an average 20% to 25% weight loss among clinical trial patientsPatients experienced a significant improvement in knee pain and mobility.TUESDAY, Nov. 10, 2026 (HealthDay News) — An experimental weight-loss drug could help ease pain and improve mobility for people with knee arthritis, a new study says.About two-thirds of people taking the injectable drug, retatrutide, experienced at least a 50% reduction in knee pain, researchers reported Nov. 8 in The New England Journal of Medicine.People on retatrutide lost an average 20% to 25% of their initial body weight, lowering the amount of stress that everyday movement places on their knees, researchers said.“The findings are really saying for people who are overweight and have osteoarthritis, if you lose a significant amount of weight with this treatment, there is a good chance that you’re going to get a meaningful reduction in your knee pain,” lead researcher Dr. Thomas Schnitzer said in a news release. He’s a professor of physical medicine and rehabilitation, anesthesiology and medicine at Northwestern University Feinberg School of Medicine in Chicago.“A major factor is that you’re loading your knees less and therefore, there’s less pain and it allows you to increase your function,” Schnitzer said.Retatrutide belongs to the newer class of GLP-1 weight-loss drugs, alongside semaglutide (Ozempic/Wegovy) and tirzepatide (Mounjaro/Zepbound).Glucagon-like peptide-1 (GLP-1) drugs mimic the GLP-1 hormone, which helps control insulin and blood sugar levels, decreases appetite and slows digestion of food.However, retatrutide targets three different hormones known to influence hunger and appetite, compared to one for semaglutide and two for tirzepatide, researchers said.Because of this, retatrutide outpaced the 10% to 20% weight loss that typically results from treatment with semaglutide or tirzepatide, researchers said.For the new study, researchers analyzed data from two clinical trials involving more than 1,000 patients. In the trials, people were randomly chosen to receive either retatrutide or a placebo.All patients had a body mass index (BMI) of 27 or greater, classifying them as either overweight or obese, and had been diagnosed with painful knee arthritis. (BMI is an estimate of body fat based on height and weight.) None had diabetes.Results showed that 63% to 70% of people taking retatrutide experienced at least a 50% reduction in knee pain, compared to 38% of those on a placebo.About 64% to 65% of retatrutide patients also had a 50% improvement in knee function, compared with 33% of those taking a placebo, the study found.This improvement was directly tied to patients’ weight loss, researchers said.“Participants had remarkable responses,” Schnitzer said. “Many of the people in this study lost considerable amounts of weight, with a few losing up to a hundred pounds or more.”GI symptoms like nausea, diarrhea and constipation were the most common side effects among people taking retatrutide. About 4% to 8% of patients had to stop taking the drug due to these GI side effects, depending on their dosage.Patients whose weight is contributing to knee pain should start off with diet, exercise and other lifestyle changes to try to lessen the impact of their arthritis, Schnitzer said.The next step in research will be to see if retatrutide slows the progression of arthritis enough to forestall knee replacement surgery, researchers said.“That would be the goal here to say you can reduce people’s pain, and you can stop the progression of their osteoarthritis,” Schnitzer said.Researchers also want to investigate whether the drugs could help knee arthritis pain in people who don’t have excess weight.“These drugs are believed to have significant anti-inflammatory activity, but the mechanism is not entirely known,” Schnitzer said.“Whether cutting down inflammation in the joint is also important in addition to reducing load needs more research, so this is still a first step, in my view,” he continued. “I’ve been working in the osteoarthritis field for a long time, and I think this opens up opportunities to do a lot more studies to understand the condition better.”The drug’s developer, Eli Lilly, funded the clinical trials.Retatrutide has not been approved by the U.S. Food and Drug Administration. More informationHarvard Medical School has more on GLP-1 drugs and knee arthritis.SOURCES: Northwestern University, news release, Nov. 8, 2026; The New England Journal of Medicine, Nov. 8, 2026 .What This Means For YouPatients carrying extra weight with knee arthritis should talk to their doctor about whether a GLP-1 drug could help reduce their joint pain..Sign up for our weekly HealthDay newsletter

Experimental Weight-Loss Drug Eased Knee Pain Among Arthritis Sufferers, Clinical Trials Show

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