Diabetes drug tackles knee osteoarthritis pain, pushing surgery down the line

A widely used diabetes medicine has shown promise in reducing knee osteoarthritis pain in individuals with overweight or obesity, potentially delaying the need for knee replacement surgery.

In the randomised clinical trial, Monash University researchers examined whether metformin – prescribed for type 2 diabetes – in comparison to a placebo, could reduce knee pain in patients with symptomatic knee osteoarthritis and concurrent overweight or obesity. The results were promising: participants in the metformin group reported a 31.3-point reduction in pain after six months, significantly outpacing the placebo group’s 18.9-point reduction.

Lead researcher, Professor Flavia Cicuttini, Head of Monash University’s Musculoskeletal Unit and The Alfred’s Head of Rheumatology, emphasised the potential of metformin as an affordable and accessible treatment option for symptomatic knee osteoarthritis pain.

There have been no new osteoarthritis drug approvals in Australia since the late 1990s, following the introduction of Celebrex (celecoxib) and Vioxx (rofecoxib), with the latter being withdrawn from the market in 2004. Other treatments, such as exercise, weight loss, and medications like paracetamol or anti-inflammatory creams, offer only modest benefits.

As knee osteoarthritis remains challenging to treat effectively, many patients and clinicians turn to alternative solutions, including surgery. This trend has contributed to a significant rise in knee replacements for individuals with early-stage osteoarthritis. However, this approach is not without its issues.

“At first glance this may seem reasonable, but it is a major problem because patient dissatisfaction with knee replacements is already high at between 20%-30%, even when the operation is technically perfect,” Professor Cicuttini explained. “Dissatisfaction rates are highest when the operation is done for early knee osteoarthritis.”

Additionally, Professor Cicuttini said that early surgeries can lead to the need for repeat procedures, which are not only costly – approximately $70,000 compared to $20,000 for an initial surgery – but also tend to deliver inferior results.

Given these complications, Professor Cicuttini stressed that the ideal outcome for patients is to delay knee replacements until absolutely necessary.

“GPs are very familiar with metformin, which is a low-cost, safe medication. It could be provided to patients in addition to other treatments they use and has the potential to delay people having knee replacements before they are absolutely needed. If people on metformin have less knee pain and are able to do more physical activity, then knee replacements can wait,” she added.

Professor Cicuttini and her colleagues are working to integrate metformin into the knee osteoarthritis management pathway in collaboration with healthcare professionals, including GPs and orthopaedic surgeons. Although metformin is not yet officially approved for knee osteoarthritis, it could be prescribed ‘off-label’ after discussion between patients and their healthcare professionals.

“Metformin is safe and well tolerated,” she said. “It is used safely in other non-diabetes conditions such as polycystic ovarian syndrome. Metformin could be provided simply and safely using a telehealth approach, as we did in our study, meaning that it could be provided across the community, including in regional and remote areas.”

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