Relationship between early physical activity after total knee arthroplasty and postoperative physical function: are these related?

BACKGROUND: Physical activity is associated with physical function; however, the relationship between early physical activity after total knee arthroplasty (TKA) and postoperative physical function remains unclear. The purpose of this study was to evaluate the association of early physical activity after TKA with postoperative physical function. METHODS: Timed Up and Go test (TUG) of 47 patients was assessed preoperatively and at 10 days, 3 months, and 6 months postoperatively. Physical activity from the second to the ninth day after TKA was measured with accelerometer, and the correlation with pre- and postoperative physical function was evaluated . A multiple linear regression was used to predict TUG at 6 months after TKA. RESULTS: Postoperative physical activity correlated with preoperative TUG (ρ = −0.485, p < 0.001), TUG at 10 days (ρ = −0.675, p < 0.001), 3 months (ρ = −0.441, p < 0.01), and 6 months (ρ = −0.368, p < 0.05) after surgery. Multiple linear regression indicated that only the preoperative TUG was associated with TUG at 6 months. Postoperative physical activity was not an independent factor predicting TUG at 6 months after TKA. CONCLUSION: Our study demonstrated that patients with better physical function have higher physical activity in the early postoperative period, whereas it does not affect physical function at 6 months after TKA. In the early postoperative period, increasing physical activity may not always be necessary to improve postoperative physical function. We also confirmed that preoperative physical function affects postoperative physical function. These findings may be beneficial in improving rehabilitation programs in the early postoperative period.