Thresholds for meaningful improvement in WOMAC scores need to be adjusted to patient characteristics after hip and knee replacement

PURPOSE: To calculate unstratified and patient-specific meaningful improvement (MI) and patient acceptable symptom states (PASS) for the WOMAC total score in patients after total hip (THR) or total knee replacement (TKR). METHODS: A retrospective observational cohort study. Anchor-based receiver operator characteristics curves were used to estimate MI and PASS thresholds. RESULTS: Recovery paths were specific to individual characteristics of patients. An unstratified 12-months MI threshold of 28.1 (PASS: 13.3) and 17.8 (PASS: 15.8) for patients after THR and TKR, respectively, would unfairly detect critical recovery paths. CONCLUSIONS: Thresholds for treatment success need to be as patient-specific as possible.