Objective: To compare the benefits of initiating rehabilitation treatment within 24 hours versus 48-72 hours after total knee arthroplasty for osteoarthritis. Design: Experimental study with clinical trial design. Subjects: Patients undergoing primary total knee arthroplasty for osteoarthritis were randomly assigned to experimental (n = 153) and control (n = 153) groups. Interventions: Rehabilitation was started within 24 hours post surgery in the experimental group and between 48 hours and 72 hours post surgery in the controls. Main measures: Measurement variables included joint range of motion, muscle strength, pain, autonomy, gait and balance. Results: In comparison with the controls, the experimental group showed significantly shorter hospital stay (by (mean +/- standard deviation) 2.09 +/- 1.45 days; P<0.001), fewer rehabilitation sessions until medical discharge (by 4.95 +/- 2.34; P<0.001), lesser pain (by 2.36 +/- 2.47 points; P<0.027), greater joint range of motion in flexion (by 16.29 +/- 11.39 degrees; P<0.012) and extension (by 2.12 +/- 3.19; P<0.035), improved strength in quadriceps (by 0.98 +/- 0.54; P<0.042) and hamstring muscles (by 1.05 +/- 0.72; P<0.041), and higher scores for gait (P<0.047) and balance (P<0.045). Conclusion: Initiation of rehabilitation within 24 hours after total knee arthroplasty reduces the mean hospital stay and number of sessions required to achieve autonomy and normal gait and balance.