Purpose: There is insufficient evidence regarding the precise levels of physical activity (PA) in older patients following total knee arthroplasty (TKA). The aims of this study were (1) to describe the changes in the amount and intensity of PA before and after TKA with an accelerometer in older patients, compared with age- and sex-matched healthy participants and (2) to assess the effect of TKA on PA depending on age. Methods: Sixty-six primary TKA patients aged 60 years or over (mean age, 73.3 years) wore an accelerometer (Lifecorder EX) for 10 consecutive days and completed the Oxford Knee Score (OKS) before and at 6 months after TKA. PA was evaluated by mean step count and time spent (min) engaged in PA per day. PA intensity was classified as light (1.5–3 metabolic equivalents (METs)), moderate to vigorous (≥3 METs), and total (≥1.5 METs). Sixty-four healthy participants completed a single assessment of PA. Results: Each of the PA measures and OKS increased significantly after TKA. Compared with healthy controls, light and total PA improved to 100% at 6 months after TKA in patients 75 years or older. By contrast, moderate-to-vigorous PA was 32% of that of the controls and rose to 78% after TKA. PA intensity in patients aged 60–74 years was 31–74% of the controls but did not reach the same level after TKA. Conclusion: TKA in older patients increases the amount of PA, with light and total PA suitable parameters for assessing PA.
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