Millions of people live with knee osteoarthritis, a condition that slowly wears away the protective cartilage inside the knee joint.
As the cartilage becomes damaged, the bones rub together more easily, leading to pain, stiffness, swelling, and difficulty walking.
The condition is especially common in older adults, but it can also affect younger people after injuries or because of excess body weight. Many people rely on pain medicines, yet these drugs may cause unwanted side effects when used for long periods.
A new clinical trial suggests that improving gut health may offer another way to reduce knee pain. Researchers from the University of Nottingham tested whether a daily prebiotic fibre supplement called inulin could help people with knee osteoarthritis.
Their findings were published in the journal Nutrients and point to a simple dietary approach that may work alongside existing treatments.
Inulin is a natural type of fibre found in foods such as chicory root, Jerusalem artichokes, onions, garlic and asparagus. Unlike ordinary carbohydrates, it is not digested in the small intestine. Instead, it reaches the large intestine, where it becomes food for helpful gut bacteria.
When these healthy bacteria break down inulin, they produce substances called short-chain fatty acids. One of the most important is butyrate, which has been linked with lower inflammation and healthier communication between the gut, immune system and nervous system. Scientists believe these effects may influence how the body experiences pain.
The INSPIRE trial included 117 adults with knee osteoarthritis. Participants were randomly assigned to receive inulin, a digital physiotherapy-supported exercise program, both treatments together, or a placebo for six weeks. Because the study was randomised and controlled, it provides stronger evidence than simple observation alone.
The results showed that people taking inulin reported less knee pain. They also had stronger hand grip and became less sensitive to pain than before the study. Interestingly, both inulin and physiotherapy helped reduce knee pain, but only the inulin group showed improvements in grip strength and pain sensitivity.
The researchers also measured biological changes. People taking inulin had higher levels of butyrate and a gut hormone called GLP-1. Higher GLP-1 levels were linked with better grip strength, suggesting that gut health may influence muscle function as well as pain.
Another important finding was that very few people stopped taking the fibre supplement. Only a small percentage left the inulin group, while many more dropped out of the physiotherapy program.
This suggests that adding a supplement to breakfast or yoghurt may be easier for some people than sticking to an exercise routine, although exercise remains an important part of arthritis care.
The researchers stressed that inulin is not a cure for osteoarthritis. People should continue following medical advice, staying active, maintaining a healthy weight and using prescribed treatments when needed. However, this study suggests that improving gut health may become another useful tool for managing symptoms.
This early research is encouraging because it explores a treatment that is simple, affordable and generally well tolerated. The study was relatively short and larger, longer trials are still needed to confirm the benefits and determine who is most likely to respond.
Even so, the findings provide growing evidence that the bacteria living in our gut may influence pain, muscle strength and healthy ageing in ways scientists are only beginning to understand.
Review and analysis: This was a well-designed randomised clinical trial, giving the findings reasonable strength.
The improvements in pain, grip strength and low dropout rate make the results promising, but the study lasted only six weeks. More research involving larger and more diverse groups is needed before inulin can be recommended as a standard treatment for knee osteoarthritis.
If you care about health, please read studies that plant-based diets can harm your bone health without these nutrients, and how to ease arthritis with anti-inflammatory foods.
For more health information, please see recent studies that too much of this vitamin may increase your risk of bone fractures, and results showing this type of exercise may protect your bone health, slow down bone aging.
Source: University of Nottingham.
