Preoperative range of motion as a predictor of postoperative outcomes in total knee arthroplasty under enhanced recovery after surgery protocols: Defining clinically relevant cut-offs

Background: The predictive role of preoperative range of motion (ROM) in total knee arthroplasty (TKA) under Enhanced Recovery After Surgery (ERAS) protocols remains underexplored. Objective: To identify clinically relevant preoperative ROM thresholds predictive of suboptimal postoperative motion in ERAS-based TKA. Methods: A retrospective cohort of 339 TKA patients managed under ERAS was analyzed. Preoperative ROM in extension (ROMS) and flexion (ROME) were assessed as predictors of postoperative ROM and functional outcomes. Correlation, regression, and ROC analyses were performed. Results: A preoperative ROMS cut-off of 30° demonstrated 100 % specificity for predicting poor postoperative extension (>10°) and flexion (<100°) (AUC = 0.361 and 0.420, respectively). Preoperative ROME predicted postoperative flexion with higher accuracy (AUC = 0.778) and an optimal threshold of 150°, achieving 100 % sensitivity and 99.6 % specificity. Preoperative ROM parameters, however, showed limited correlation with functional scores and patient-reported outcomes. Conclusion: A 30-degree preoperative ROMS serves as a highly specific predictor of postoperative ROM limitation, offering an actionable benchmark for patient selection and perioperative planning within ERAS pathways. Level of evidence: Level III, Retrospective cohort study.