Minimal Clinically Important Differences in Short-Term Postoperative Knee Injury and Osteoarthritis Outcome Score (KOOS) after Total Knee Arthroplasty: A Prospective Cohort Study

Background/Purpose: The purpose of this study was to determine the short-term minimal clinically important differences (MCIDs) in Knee injury and Osteoarthritis Outcome Score (KOOS) after total knee arthroplasty (TKA) using the anchor method. Methods: Scores for each KOOS subscale were calculated preoperatively and 3 and 6 months postoperatively to create receiver operating characteristic curves, and the MCIDs were calculated. Results: The KOOS MCIDs at 3 months after TKA were 6 for symptoms, 10 for pain, 6 for activities of daily living (ADL), 8 for sport/recreation, and 10 for quality of life (QOL). The KOOS MCIDs at 6 months after TKA were 9 for symptoms, 13 for pain, 10 for ADL, 9 for sport/recreation, and 16 for QOL. The areas under the curves were in the range of 0.8–0.9 at both 3 and 6 months after TKA. Conclusion: MCIDs by KOOS subscales were determined and were highly accurate.