Accelerometer-measured postoperative physical activity confers a significant mortality benefit following joint arthroplasty

Aims: The aim of this study was to examine the association between postoperative physical activity and mortality following hip and knee arthroplasty. Methods: A retrospective cohort study was conducted using the UK Biobank dataset, linked to hospital and death registry data. Adults undergoing hip or knee arthroplasty with valid postoperative accelerometer data were included. Physical activity (PA) metrics, including daily step count, light PA, moderate-to-vigorous PA, Euclidean Norm Minus One (ENMO), and peak cadence, were derived using a machine-learning algorithm. Survival probability was assessed up to 20 years postoperatively using Cox regression models. Results: A total of 1,769 patients were included. Between the ten- and 20-year follow-ups, higher PA was associated with reduced all-cause mortality. Multiple Cox regression highlighted that adjusted daily step count (HR 0.92, 95% CI 0.87 to 0.97; p = 0.004), light PA (HR 0.86, 95% CI 0.760 to 0.98; p = 0.020), moderate-to-vigorous PA (HR 0.64, 95% CI 0.42 to 0.97; p = 0.036), ENMO (HR 0.97, 95% CI 0.94 to 1.00; p = 0.030), and peak cadence (HR 0.98, 95% CI 0.97 to 0.99; p = 0.001) were significantly associated with reduced all-cause mortality. Conclusion: This is the first study to demonstrate that objectively measured postoperative PA predicts long-term survival following hip and knee arthroplasty. These findings highlight the importance of PA and careful procedure selection in maximizing long-term outcomes.