The annual healthcare cost of total knee and hip replacements (TKR and THR) due to osteoarthritis in Australia is expected to reach A$5.32 billion by 2030. While associations between osteoarthritis and obesity are well-established, and while inter/national osteoarthritis guidelines recommend weight loss for patients with overweight/obesity, the effects of weight loss on progression to joint replacement are unknown. We aimed to determine the effect of weight change on the risk of TKR and THR.
Using data from the Osteoarthritis Initiative, a multicenter, prospective observational study which collected data over 10 years from adults aged 45-79 years who had or were at risk of clinically significant knee osteoarthritis at baseline, we conducted a time-to-event survival analysis to determine the effect of weight change on TKR and THR.
A total of 8,069 knees and 8,076 hips from 4,081 and 4,064 participants (59.3% female) with mean (SD) baseline body mass index (BMI) of 28.7 (4.8) kg/m2 were included in the TKR and THR analyses, respectively. Weight change had a small, positive, dose-responsive effect on the risk of TKR (hazard ratio [HR] 1.02; 95% CI, 1.00-1.04, p=0.025). Weight change also had a small, positive, dose-responsive effect on the risk of THR, but only in people with radiographic evidence of hip osteoarthritis at baseline, and the effect was only borderline significant (HR 1.03; 95% CI, 1.00-1.07, p=0.058). There was no significant interaction between baseline BMI and weight change in effects on joint replacement.
For every 1 kg of weight lost, regardless of starting BMI, the risk of TKR was reduced by 2%. Weight loss also seemed to reduce the risk of THR in people with existing signs of hip osteoarthritis. This has potential implications for incorporating weight loss interventions into public health strategies to reduce the burden of joint replacement surgery.