This single-center cohort study examined how certain preoperative factors — such as overall physical capability and the size and tissue composition of the quadriceps femoris — relate to physical activity (PA) levels measured 1 year after total knee arthroplasty (TKA). A total of 204 patients with knee osteoarthritis who underwent TKA were included and later divided into two groups based on whether their physical activity increased or decreased. Variables that showed notable differences between these groups (non-operative-side quadriceps strength, knee injury, and osteoarthritis outcome score (KOOS) Sport/Rec subscale, operative-side cross-sectional area (CSA) of the vastus medialis (VM), and operative-side computed tomography attenuation value (CTV) of the vastus lateralis (VL)) were entered into a multiple logistic regression analysis. Using the receiver operating characteristic (ROC) curve, researchers calculated the preoperative VM CSA cutoff value needed for patients to achieve adequate PA points at the one-year postoperative mark.The multivariate logistic regression analysis indicated that non-operative-side quadriceps strength, KOOS Sport/Rec score, operative-side CSA of the VM, and operative-side CTV of the VL were independently linked to higher physical activity following TKA. The ROC analysis produced a cutoff value of 10.2 cm².The results imply that the amount and condition of muscle tissue before surgery, especially in the vastus medialis, exert considerable influence on physical activity outcomes one year after TKA.
