Average Age for Knee Replacement Surgery Is Dropping Due to

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New research finds that increases in rates of obesity are leading to more people needing total knee replacements at a younger age. Getty Images
  • The number of total knee replacement surgeries is growing larger every year, with even more expected over time.
  • Research suggests that the leading cause is the rise in rates of obesity.
  • Excess weight can put increased stress on knees, leading to joint injuries.
  • Medical experts say modest weight loss significantly improves the symptoms of knee osteoarthritis and reduces the risk of needing a knee replacement.

As the number of total knee replacement (TKR) surgeries continue to climb, a study out of Queensland, Australia points at a possible major cause — and with it a possible solution.

Obesity and weight gain, the study found, is both increasing the amount of TKR’s done, as well as driving down the average age of the recipient.

Using data from the Australian Bureau of Statistics’ (ABS) 2017-18 National Health Survey with the Australian Orthopaedic Association National Joint Replacement Registry, researchers found that, of the 56,217 Australian TKR patients in that time frame, 57.7 percent were obese.

TKR patients who were obese were also an average of seven years younger than patients who were not obese.

Additionally, women ages 55 to 64 with obesity were 17 times more likely to need TKR than those who were not obese.

Men living with obesity were 5.8 times more likely to need TKR than their peers who were not obese.

Those statistics ring true, orthopedic surgeons say.

“We have a silent impending epidemic,” Dr. Scott Oliver, orthopedic surgery specialist at Beth Israel Deaconess Plymouth in Massachusetts, told Healthline.

“And with obesity projected to continue to increase, this is only going to increase as well,” he said.

Oliver said weight has a particular impact on the knee joint, even more so than the hip.

He said that four things often lead to knee joint damage. They are genetics, overuse, trauma, and excessive weight. He added that these things can damage joints in any combination together or individually.

The general statement, he said, is that every added pound over a healthy weight can add four pounds of pressure to a weight-bearing joint like the knee.

“We see it more and more in younger people, and it’s not going away,” he said.

That’s what inspired Dr. Chris Wall, deputy director of the Department of Orthopaedics at Queensland College, to conduct the study.

A large proportion of the patients that I see in clinic with knee osteoarthritis are obese. Similarly, a large proportion of patients that I perform knee replacements on are obese. This sparked my interest,” he said.

Why does weight impact the knee joint so profoundly? Wall said the answer isn’t as clear cut as people may think.

“The traditional theory was that excess body weight affected the knee in a purely mechanical fashion. However, recent research has demonstrated that the association between obesity and knee osteoarthritis is much more complex. The association is still not fully understood, but it is probably a combination of genetic, biochemical and metabolic factors, as well as mechanical overload,” he explained.

Despite the rising need for knee TKR surgeries, Wall said the study does highlight potential good news too: prevention can help reduce the risk.

“Previous research has shown that modest weight loss — 10 percent of body weight — significantly improves the symptoms of knee osteoarthritis and reduces the risk of needing a knee replacement,” Wall said.

He said he’s met many patients with obesity and knee osteoarthritis who lost some weight and their knee symptoms improved to the point that they no longer needed a knee replacement.

Oliver also pointed out that there are four primary ways obesity can be treated to help reduce the risk of necessary TKR surgeries. They are: medications, injections, physical therapy and weight reduction.

He said that surgery should always be a “last resort,” reiterating that weight loss can often “slow down or stop progression” toward needing a TKR if action is taken early enough.

Both Wall and Oliver pointed out that TKR surgery alone can’t fix the issue. If a person’s obesity isn’t treated, the extra weight will wear down the newly replaced joint.

“Unfortunately, obesity increases the risk of short-term and long-term complications after knee replacement,” Wall said.

Among the potential complications is the risk of infection after TKR surgery, which is ten times higher for those who are living with obesity.

Oliver said this can mean way more than simply needing an extra round of antibiotics. In many cases, an infection will require the TKR to be removed and replaced with another surgery.

He said these concerns are often part of the dilemma with TKR surgeries for people with obesity.

“We don’t want to put the patient at risk,” he said.

Oliver said he feels that treating obesity is the key to reducing the need for TKR surgeries. He pointed to research which projects that knee injuries due to obesity will soar to 70 percent by the end of the decade.

“We are seeing it in younger and younger people, and it’s not going away,” he said.

Wall agreed that it’s a challenge that needs attention and action at a higher level.

“I think the key message is that we need to address the issue of obesity at a population level, including a strong focus on prevention,” he said.