Obese individuals may need knee replacement surgery at a younger age than normal-weight patients

/ 07:41 PM April 12, 2020
weighing scale

Being obese may increase the risk of needing knee replacement surgery. Image: iStock/Tsuji via AFP Relaxnews

New Australian research has found that individuals who are obese may need knee-replacement surgery much sooner than regular-weight patients.

Led by The University of Western Australia and Fiona Stanley Hospital, the new study looked at data on 41,023 patients gathered from the Australian Orthopaedic Association National Joint Replacement Registry.


The patients were categorized into groups based on body mass index (BMI), which was calculated using the World Health Organization’s definitions.

The findings, published in the journal Annals of the Rheumatic Diseases, showed that 57% of the participants who had knee replacements were obese, and those who were the most obese had knee replacement surgery an average of eight years earlier than those in the regular weight group.


Even being overweight appeared to affect how soon patients needed surgery, with overweight patients having their knees replaced nearly two years earlier, on average, than patients with normal weight.

After microscopic examination, the researchers also found that obese patients were more likely to experience horizontal fissuring, which is when the area between the cartilage and bone breaks down, due to the increased pressure from carrying extra weight. An increase in one unit of BMI (one kilogram per square meter) increased the chance of horizontal fissures by 14.7%, with the team finding that 84.4% of the horizontal fissures could be attributed to obesity.

Lead author Professor Ming-Hao Zheng, pointed out that obesity is a well-known risk factor for osteoarthritis, however, there has been less research investigating the link between obesity and joint replacement.

“In this study we set out to learn more about this by examining the link between a person’s BMI and the age at which people undergo knee replacements,” Zheng said. “The data revealed that 80% of the obese patients had a knee replacement due to horizontal fissuring.”

“This was different to the reason regular-weight patients sought knee replacements — instead they underwent surgery mainly due to cartilage damage from normal wear and tear to a joint.”

“This means obese patients are most likely to require further replacement of prosthetic implant as the lifespan of the prosthesis is less than maximum of 15 years,” said Zheng, adding that, “the findings will also help us understand and predict the age at which a person might be prone to horizontal fissuring.” RGA



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TOPICS: Australia, body mass index, body weight, knee, obesity
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