Interactive combinations between gait speed and physical function at acute phase can predict the physical activity at two-year after total knee arthroplasty using classification and regression tree analysis

Published:January 24, 2023DOI:



      To clarify the interactive combinations of various clinical factors associated with physical activity (PA) at 2 years after total knee arthroplasty (TKA) using classification and regression tree (CART) analysis.


      A retrospective cohort study.


      A single university hospital.


      286 patients who underwent TKA.

      Main outcome measures

      PA was assessed preoperatively, 3 weeks, and 2 years after TKA. Physical functions, namely 10m walking test (10MWT), Timed-up and Go test, one-leg standing time, isometric knee extension and flexion strength, knee joint stability, knee pain, femora-tibial angle, and the passive knee extension and flexion angle, were measured before surgery as a baseline and 3 weeks after TKA as acute phase. CART analysis was conducted to clarify the interactive combinations that accurately predict the PA at 2 years after TKA.


      The results of CART analysis indicated that gait speed (≥ 1.05 m/s) at the acute phase after TKA was the primal predictor for the postoperative PA at 2 years. The highest postoperative PA at 2 years was determined by gait speed (≥ 1.05 m/s) and PA (>74.5) at the acute phase. The PA at baseline and at acute phase, as well as the BMI were also selected as predictors of postoperative PA at 2 years.


      The present study suggested that acquiring gait speed (≥ 1.05 m/s) and PA (>74.5) in the postoperative acute phase is the predictive of a high PA at 2 years after TKA.

      Key words

      List of abbreviations:

      TKA (Total knee arthroplasty), PA (physical activity), QOL (quality of life), BMI (body mass index), CART (classification and regression tree), 10MWT (10m walking test), TUG (Timed-up and Go test), OLS (one-leg standing), FTA (femora-tibial angle), ANOVA (analysis of variance), R2 (coefficient of determination)
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