More than half of Australians who underwent knee replacement (KR) for osteoarthritis (OA) were living with obesity, increasing their risk of having the operation at a younger age, especially among women. According to a study by The University of Queensland Rural Clinical School (UQRCS) that compared data from the Australian Bureau of Statistics' (ABS) 2017-18 National Health Survey with the Australian Orthopaedic Association National Joint Replacement Registry, of the 56, 217 patients who underwent a knee replacement for OA, 57.7% were living with obesity.
Around 2.2 million Australians have OA and nearly a-third of adults have obesity, according to the ABS. The findings were featured in the paper, ‘Obesity is associated with an increased risk of undergoing knee replacement in Australia’, published in the ANZ Journal of Surgery.
"Obese women aged 55–64 years were up to 17.3 times more likely to undergo a knee replacement than their healthy weight counterparts, while obese men in the same age group were up to 5.8 times more likely," said UQRCS Head of Research, Associate Professor, Srinivas Kondalsamy-Chennakesavan, who explained that the risk of knee replacement for OA was relative to a person's body mass index (BMI). "Obese patients with the highest BMI ratio were also seven years younger on average when they had a knee replacement, compared to normal weight individuals."
The relative risk of undergoing KR for OA increased with increasing BMI category. Class 1, 2 and 3 females with obesity aged 55–64 years were 4.7, 8.4 and 17.3 times more likely to undergo KR than their normal weight counterparts, respectively. Males in the same age and BMI categories were 3.4, 4.5 and 5.8 times more likely to undergo KR, respectively. Class 3 patients with obesity underwent KR 7 years younger, on average, than normal weight individuals.
"Modest weight loss has been found to effectively reduce knee OA symptoms, and obese patients who maintained a 10% body weight loss experienced significant improvement in pain and function," said lead investigator, Dr Chris Wall. "By 2030, it's expected more than 161 thousand knee replacements will be conducted annually. Urgent action is needed at a national level to change our approach towards reducing obesity or Australia may face a growing burden of revision knee replacement in the future."
This study was conducted in collaboration with Professor Richard de Steiger, Professor Christopher Vertullo, Dr. James Stoney, Professor Stephen Graves, and Ms Michelle Lorimer.