Timing Matters: Early Versus Delayed Rehabilitation After Total Knee Arthroplasty and Its Impact on Functional Recovery—A Systematic Review

Background: Total knee arthroplasty (TKA) is widely used to treat advanced knee osteoarthritis, yet the optimal timing for initiating postoperative rehabilitation remains unclear, particularly regarding its impact on short- and long-term functional outcomes. Objective: This study aimed to systematically review and compare earlier versus later initiation of structured postoperative rehabilitation following primary TKA according to the timing definitions used in the available literature of structured postoperative rehabilitation after primary TKA and its effects on functional recovery. Methods: Electronic searches were performed in PubMed, Scopus, Web of Science, and ScienceDirect between January and February 2025. Studies were limited to human participants, published in English or Spanish from 2010 onwards. Eligible studies compared early versus delayed rehabilitation following primary TKA and reported at least one predefined outcome related to pain, patient-reported functional measures, range of motion, muscle strength, performance-based functional tests, or hospital length of stay. Study selection was performed independently by two reviewers, and methodological quality was assessed using the Joanna Briggs Institute critical appraisal tools. Results: A total of 662 records were identified, of which five studies (three randomized controlled trials, one prospective observational study, and one retrospective cohort study), including 185 participants, met the inclusion criteria. Early rehabilitation (typically initiated within the first postoperative hours to days) was associated with reductions in hospital length of stay ranging from approximately 1 to 2 days, lower early postoperative pain scores, greater short-term knee flexion gains, and improved early muscle strength compared with delayed rehabilitation protocols. However, no consistent differences were observed in medium- and long-term patient-reported functional outcomes across studies. No increase in postoperative complications was reported. Conclusions: Early initiation of rehabilitation after TKA appears safe and may enhance short-term recovery outcomes. However, no consistent long-term functional differences were observed between earlier and later rehabilitation initiation across the included studies. Further high-quality research with standardized definitions and long-term follow-up is required.