Weight loss reduces risk of total knee and hip replacement in obese adults: Study

Australia: Weight loss target >7.5% is needed to reduce total knee replacement (TKR) risk in adults with overweight or obesity, a recent study in the International Journal of Obesity has found. According to the authors, weight gain should be avoided as it increases the risk of THR.

Total knee replacement is a risky surgery affecting the quality of life to a greater extent. Large weight-bearing joints, notably the knee and hip, are usually affected by osteoarthritis in people aged 45 and above. A new study by Xingzhong Jin and the team has pointed that Obesity is a well-recognized risk factor for the development and progression of osteoarthritis (OA), and likely adds to the necessity for total knee replacement in the older patient. 

The objective of the study was to investigate the association between weight change and total knee or hip replacement (TKR or THR) for OA among middle-aged and older adults with overweight or obesity. The global economic burden of TKR and THR due to OA is high and is predicted to increase substantially in the next two decades in many countries, including the United States, United Kingdom, Canada, Sweden, and New Zealand.

The researchers collected weight data from 2006–2009 and in 2010 from the age of 45 years and above The study was a population-based cohort study aged ≥45 years in New South Wales, Australia. Participants whose baseline body mass index (BMI) ≥ 25 kg/m2 and no history of TKR or THR were included in the study. Weight change was categorised into four groups: >7.5% loss; >5–7.5% loss; stable (≤5% change) and >5% gain. Hospital admission data were linked to identify TKR and THR for OA, and multivariable Cox regression was used to assess the risk of TKR and THR.

The researchers found that out of 23,916 participants, 2139 lost >7.5% weight, 1655 lost 5–7.5% weight, and 4430 gained >5% weight. Over 5.2 years, 1009 (4.2%) underwent TKR and 483 (2.0%) THR. Compared to weight-stable, weight loss of >7.5% was associated with reduced risk of TKR after adjusting for age, sex, BMI, socioeconomic and lifestyle factors (hazard ratio 0.69, 95%CI 0.54–0.87), but had no association with THR. Weight loss of 5–7.5% was not associated with altered risk of either TKR or THR. Weight gain was associated with an increased risk of THR after adjusting for confounders, but not TKR.

The researchers concluded that "This study suggests that a weight loss target >7.5% is required to reduce the risk of TKR in adults with overweight or obesity. Weight gain should be avoided as it increases the risk of THR." They also stated future studies are needed to address the limitations of this study. In particular, the weight loss target >7.5% should be further confirmed in clinical trials or in long-term epidemiology studies in an OA population, such as the Osteoarthritis Initiative.

For further information:

Xingzhong Jin, Alice A. Gibson, Joanne Gale, Francisco Schneuer, Ding Ding, Lyn March, Amanda Sainsbury & Natasha Nassar "Does weight loss reduce the incidence of total knee and hip replacement for osteoarthritis?—A prospective cohort study among middle-aged and older adults with overweight or obesity." International Journal of Obesity volume 45, pages1696–1704 (2021).