Weight-loss drugs may prevent thousands of knee replacements, study suggests | Osteoarthritis

Taking weight-loss drugs for at least three years could prevent thousands of knee replacements a year, research suggests.

Globally, more than 500 million people have osteoarthritis. Knee arthritis is the most common form, affecting about 14 million people in the US and more than 5 million in the UK. Many will require knee surgery. In the UK more than 120,000 knee replacements are carried out every year.

Being overweight or obese significantly increases the risk of developing knee arthritis, by placing greater load on the joints.

Previous studies have found that weight-loss drugs can help reduce the pain from knee osteoarthritis. Now researchers have found that taking medications such as Mounjaro and Wegovy, or those for type 2 diabetes such as Ozempic, could also help prevent the need for knee surgery.

Experts at the University of Maryland School of Medicine in the US examined data for 6.8 million adults diagnosed with knee osteoarthritis between 2010 and 2024.

They then identified a matched sample of 42,000 people who had been taking any type of GLP-1 medication for at least one year, who were compared with an equal number of similar patients who had not. They also analysed data for just under 31,000 patients who had been taking the drugs for three years.

Patients were tracked at regular intervals for eight years after diagnosis to assess the need for knee replacement surgery.

The study, published in Regional Anesthesia & Pain Medicine, found that taking GLP-1 medications for one year was associated with a 1.4-percentage-point reduced risk of knee replacement surgery at the three-year follow-up point and a 2.8-percentage-point lower risk after eight years.

But the greatest reduction in risk was with newer weight-loss drugs and longer treatment. Taking semaglutide or tirzepatide for three years was associated with a nearly 5-percentage-point lower chance of needing knee replacement at the eight-year follow-up assessment.

The authors speculated that, if all eligible patients with knee arthritis and obesity or metabolic disease took semaglutide or tirzepatide for three years, there could be up to 14,400 fewer knee replacements every year in the US and more than 1,500 a year fewer in the UK.

“Our findings align with evidence that GLP-1 [receptor agonists] may influence knee [osteoarthritis] through complementary anti-inflammatory and analgesic mechanisms,” they conclude.

Responding to the findings, Mark Bowditch, a consultant knee surgeon and immediate past president of the British Orthopaedic Association, said there may be some “direct anti-inflammatory and possibly cartilage-protective effects of GLP-1 receptor agonists that operate through weight-independent mechanisms”. But he also urged caution, as the findings do not prove that these drugs prevent the need for surgery.

“GLP-1 receptor agonists are not approved for the treatment of osteoarthritis, and we would strongly caution against their use for this purpose outside of clinical trials,” he said.

Prof Lucy Donaldson, director of research at Arthritis UK, said the findings could help better understand the potential impact of weight-loss medications to help some patients avoid or delay the need for joint replacement surgery.

“Maintaining a healthy weight can play a vital role in managing osteoarthritis, particularly in weight-bearing joints such as the knees and hips,” she said. “For those able [to stay active and mobile], even a small amount of weight loss can improve symptoms and sometimes slow the progression of osteoarthritis.”