Introduction: The annual healthcare cost of total knee replacement surgery due to osteoarthritis in Australia is expected to reach A$3.40 billion by 2030. While osteoarthritis is clearly associated with obesity, and inter/national osteoarthritis guidelines recommend patients with overweight/obesity lose weight for symptom reduction, the effect of weight loss on progression to knee replacement is unclear.
Materials and methods: Using data from 3 cohorts of people with or at risk of clinically significant knee osteoarthritis (the Osteoarthritis Initiative (OAI) and the Multicenter Osteoarthritis Study (MOST) from the USA, and the Cohort Hip and Cohort Knee (CHECK) study from the Netherlands), we conducted a time-to-event survival analysis with clustering of both knees per person to determine the association between change in BMI (as a proxy for weight) and the incidence of primary knee replacement over 7 to 10 years’ follow-up.
Results: A total of 16,362 knees from 8181 participants (61.5 % female), aged 45-79 years, with mean ± SD baseline BMI of 29.1 ± 5.3 kg/m2, were included in the analysis. Mean follow up was 6.9 years.
Change in BMI had a positive, dose-responsive association with the risk of knee replacement (adjusted hazard ratio 1.03; 95% confidence interval 1.00–1.06). There were no significant interactions between change in BMI and baseline BMI in the association with knee replacement. Thus, regardless of baseline BMI, every 1-unit reduction in BMI was associated with a 3% reduced risk of knee replacement. Calculation of the population attributable fraction (PAF) suggested that if people with or at risk of clinically significant knee osteoarthritis and with BMI ≥ 25 kg/m2 lost 1 BMI unit, then 3.2% (range: 0.3-5.9%) of knee replacements would be avoided.
Conclusion: Public health strategies that incorporate weight loss interventions could potentially reduce the burden of knee replacement surgery.