Put on a stone and increase odds of knee op by a third – study

Preventing weight gain in middle age could reduce the need for a knee replacement, a new study implies.

18 October 2022

People who put on just under a stone in weight in midlife are significantly more likely to need a knee replacement, a new study has found.

Women who put 11lb (5kg) are a third (34%) more likely to need a total knee replacement while men have 25% increased odds.

The new study, which is to be presented at the International Congress on Obesity in Melbourne, Australia, found that relatively small weight increases can increase a person’s chances of knee osteoarthritis, the most common cause of knee pain, and the need for a knee replacement.

Osteoarthritis is a condition that causes joints to become painful and stiff. It is the most common type of arthritis in the UK. There is no cure but there are a number of ways people can relieve symptoms including lifestyle changes and pain relief medicines.

In some cases, osteoarthritis can require joint replacement surgery.

The researchers said that guidelines recommend weight loss to manage knee osteoarthritis but not specifically recommend preventing weight gain in the first place.

“Weight loss can help ease the symptoms of knee osteoarthritis by reducing strain on the joint and lowering levels of harmful inflammation,” said Professor Anita Wluka from Monash University in Australia, who led the research.

“However, the 10%-plus reduction in total body weight that is required to have even a small effect on knee pain is difficult to achieve and even more difficult to maintain, particularly when osteoarthritis is present, reducing mobility.

“There is evidence that preventing weight gain (i.e. weight maintenance) is an easier and more achievable goal for patients than weight loss, so we set out to examine how weight gain was related to the symptoms and progression of osteoarthritis.”

Dr Wluka and her team reviewed existing research into the relationship between weight gain and knee osteoarthritis.

They analysed 20 previous studies which included hundreds of thousands of participants.

Overall weight gain appeared to have a significant detrimental effect on pain, stiffness, function, quality of life and on changes to the joint visible in X-rays.

Weight gain was also linked to more damage to cartilage, bone and other parts of the joint.

Looking specifically at two studies involving more than 250,000 participants, the authors concluded that weight gain significantly increased the odds of having a total knee replacement operation.

Dr Wluka added: “The prevention of osteoarthritis and the slowing of its progression would not only reduce the need for surgery, but it would also take pressure of the health service which, due to our ageing and increasingly obese population, is facing increasing demand for knee replacement.

“Given the challenges associated with weight loss, attention should also be paid to preventing weight gain, with individuals with osteoarthritis also given advice and support on how to maintain their current weight, something that can be particularly problematic as we get older.

“Weight maintenance in middle age would reduce the risk of knee osteoarthritis occurring and, in those with osteoarthritis, it would reduce worsening of pain, loss of function and the need for costly joint replacement.”

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