Osteoarthritis affects up to 31 million Americans, making it one of the most common conditions in the nation. The resulting joint pain can be devastating for these individuals, and the longer osteoarthritis progresses, the greater the disability becomes. It’s no surprise, then, that there is a plethora of treatments, medications, and products available that claim to alleviate pain related to osteoarthritis or even prevent it from progressing.

Over the past 20 years, glucosamine and chondroitin sulfate have emerged as two of the more popular products that claim to resolve osteoarthritis–related issues. But what are glucosamine and chondroitin sulfate, and what does the research say about their effectiveness? In this post, we try to answer these questions and help guide you towards an informed decision about whether taking these is right for you.

Glucosamine and chondroitin sulfate are naturally occurring substances that make up many connective tissues throughout the body, including the cartilage that protects the ends of bones in joints. Glucosamine is a major building block of large compounds called proteoglycans, which contributes to the elasticity of cartilage, while chondroitin sulfate is a larger molecule that also plays a key role in the elasticity and function of cartilage. Either of these chemicals can be extracted from the tissue of certain animals and then packaged in pill form—either individually or combined—to be taken as a treatment for joint pain related to osteoarthritis. The typical dose is about 1500 mg for glucosamine and 1200 mg for chondroitin sulfate, taken once daily.

However, it’s important to note that products containing glucosamine and/or chondroitin sulfate are labeled as nutritional (or dietary) supplements rather than approved medications. Status as a nutritional supplement means that these products are not subjected to the same aggressive regulations as prescription medications and claims regarding their indication or effectiveness have not been evaluated by the U.S. Food and Drug Administration (FDA). Glucosamine and chondroitin sulfate supplements typically claim to alleviate joint pain from osteoarthritis and help to slow or prevent the breakdown of joint cartilage, which is the major underlying cause of osteoarthritis pain. But do they deliver on these supposed benefits?

The short answer: possibly, but it’s difficult to say with certainty. Evidence to support glucosamine and chondroitin sulfate supplements for osteoarthritis has been mixed, with some studies suggesting that one or both chemicals can relieve pain and others identifying no clear benefits.

For example, a key analysis of multiple studies published in 2010 called a meta–analysis concluded that glucosamine and chondroitin—both independently and in combined formulations—did not reduce joint pain or have any impact on the narrowing of joint space. Another study published in 2016 that administered combined glucosamine and chondroitin sulfate to half the patients and placebo to the other half had to be stopped early because those taking the supplement reported worse symptoms than those taking placebo.

On the other hand, a 2008 study found no statistically significant improvements in knee pain overall for patients with knee osteoarthritis taking glucosamine and chondroitin sulfate supplements, but a group of patients with moderate–to–severe knee pain did experience some improvements. A 2014 review concluded that these supplements may lead to a small but significant reduction in joint space narrowing, while another key 2018 meta–analysis found that chondroitin sulfate alone was more effective than placebo for relieving pain and improving function in knee and/or hip osteoarthritis, and glucosamine was found to reduce stiffness.

Although most guidelines from professional societies do not currently recommend glucosamine and/or chondroitin sulfate for osteoarthritis, some experts believe that newer supportive research could lead to some future changes in these guidelines. But as you can see, the jury is still out on these supplements. It’s possible that the evidence is so mixed because some patients do truly experience benefits—possibly from the placebo effect, which is a real benefit nonetheless—while others do not.

Therefore, a clear–cut answer on the therapeutic value of glucosamine and chondroitin sulfate for osteoarthritis may be difficult to reach, but should you still consider taking these supplements? Since answering this question is out of our scope as physical therapists, we strongly recommend talking to your doctor and evaluating the potential benefits compared to the risks involved. These supplements are generally considered to be safe, but some side effects have been reported, including diarrhea, abdominal pain, heartburn, drowsiness, and headaches. If you and your doctor agree that the benefits outweigh the risks, it’s probably best to try a short trial of one or both supplements, and if you don’t experience any notable improvements after a designated period, consider discontinuing their use. And as always, keep realistic expectations and understand that these supplements can only go so far. Proper care for osteoarthritis also requires regular movement and exercise, and as physical therapists, we can help you get there with a comprehensive, customized treatment program.