Background: This study aimed to identify the preoperative physical performance factors that predict gait speed and endurance 1 month after total knee arthroplasty (TKA). Methods: This prospective cohort study included all patients who underwent unilateral primary TKA in December 2014-2016. Before and at 1 month after TKA, gait variables, bilateral isometric knee extensor and flexor strength, and range of motion (ROM) (flexion and extension) of the operated knee were measured; further, a 6-minute walk test (6MWT), a Timed Up and Go (TUG) test, and a stair-climbing test (SCT) were conducted. The Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), the EuroQoL 5-dimension (EQ-5D) questionnaire, and the visual analogue scale (VAS) of knee pain were also completed. Results: A total of 84 patients were included. Bivariate analyses showed that postoperative gait speed significantly and positively correlated with preoperative gait speed, gait cadence, ROM of knee flexion, and 6MWT, but significantly and negatively correlated with age and preoperative TUG test, SCT-descent, WOMAC-Function score, and VAS score. The postoperative 6MWT significantly and positively correlated with preoperative gait cadence and 6MWT, but significantly and negatively with preoperative body mass index (BMI), TUG test, SCT-ascent, and WOMAC-Function score. Linear regression analyses showed that age, preoperative ROM of knee flexion, and TUG test were independent predictors of postoperative gait speed, while preoperative BMI and 6MWT predicted postoperative 6MWT. Conclusion: These preoperative predictive factors will be useful in developing pre-and postoperative rehabilitation strategies aimed at improving gait function in the early stages after TKA.