Diabetes drug reduces knee arthritis pain in overweight patients

A common diabetes drug can reduce the pain of people with knee osteoarthritis and overweight or obesity, possibly delaying the need for knee replacements, according to a clinical trial led by Monash University and published in JAMA.

Metformin is an inexpensive, well-tolerated oral medication that has been the first-line therapy for type 2 diabetes for more than 60 years. The drug reduces the production of glucose produced and released by the liver, insulin resistance and low blood-sugar levels. It also causes modest weight loss and reduces inflammation in people with and without diabetes.

The randomised clinical trial looked at whether metformin reduced knee pain in patients with symptomatic knee osteoarthritis (knee OA) and overweight or obesity. Some of the 107 participants with pain from knee osteoarthritis, who had a mean age of 60, took up to 2000 mg of metformin daily for six months, while others took the placebo. None had diabetes.

Knee pain was measured on a 0–100 scale, with 100 being the worst. The metformin group reported a 31.3-point reduction in pain after six months, compared to 18.9 for the placebo group. This was considered a moderate effect on pain, although the researchers acknowledge that confirmation in a larger clinical trial is warranted.

Lead researcher Professor Flavia Cicuttini, who heads Monash University’s Musculoskeletal Unit, said the results are significant as effective treatments that improve knee pain in osteoarthritis are limited — no new OA drugs have been approved in Australia since the late 1990s — which has led some patients and their doctors to seek alternative treatments including surgery.

“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,” Cicuttini said. “Dissatisfaction rates are highest when the operation is done for early knee OA.

“To go through the effort and cost of a big operation like a knee replacement, only to be unhappy with the results because of ongoing pain and symptoms, is definitely low-quality care. Doing a knee replacement earlier also increases the potential need for the procedure to be redone.

“The best outcome for patients is to delay the knee replacements until it is absolutely needed.”

Cicuttini said metformin provides with GPs an alternative they can offer patients in addition to lifestyle approaches such as managing weight and increasing physical activity. She noted, “Metformin works in a number of ways on the knee, including affecting low-grade inflammation and other metabolic pathways that are important in knee OA.

“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.”

Cicuttini and her colleagues are now working with consumers, GPs, orthopaedic surgeons and other healthcare professionals to introduce metformin into the knee OA management pathway in order to improve patient outcomes. She said the drug could be provided simply and safely using a telehealth approach, following discussions between patients and their doctor, meaning that it could be provided across the community.

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