Obese patients undergo knee replacements around 8 years earlier than those who are a regular weight, researchers suggest, in Annals of the Rheumatic Diseases.

According to the study, led by researchers at The University of Western Australia and Fiona Stanley Hospital, extra body weight causes a pathological change of the knee called horizontal fissuring, where the area between the cartilage and bone breaks down due to the increased pressure from carrying weight.

Although obesity was well-recognized as a key risk factor in osteoarthritis, the link between obesity and joint replacement was less understood, says lead author Professor Ming-Hao Zheng, Associate Dean of UWA’s Faculty of Health and Medical Sciences, in a media release from University of Western Australia.

“In this study we set out to learn more about this by examining the link between a person’s body mass index and the age at which people undergo knee replacements,” Zheng says.

“We analyzed data collected from the Australian Orthopaedic Association National Joint Replacement Registry from 40,000 Australian patients. Then we categorized patients by their body mass index using the World Health Organization’s definitions to determine those who were regular weight, and those who were obese, and the level of obesity.”

According to Zheng, the researchers found 57% of participants who had knee replacements were obese and on average had the replacements done 8 years earlier than regular-weight patients.

“The data revealed that 80 percent of the obese patients had a knee replacement due to horizontal fissuring,” he adds.

“This was different to the reason regular-weight patients who 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,” he suggests.

“The findings also help us understand and predict the age at which a person might be prone to horizontal fissuring,” Zheng concludes.

[Source(s): University of Western Australia, MedicalXPress]