Diagnosis-Specific Thresholds of the Minimal Clinically Important Difference and Patient Acceptable Symptom State for KOOS After Total Knee Arthroplasty
Authors: Emara Ahmed K. , Pasqualini Ignacio , Jin Yuxuan , Klika Alison K. , Orr Melissa N. , Rullán Pedro J. , Piuzzi Nicolas S. ,   the Cleveland Clinic Arthroplasty Group
Published: February 2024

Update:
This article was updated on May 1, 2024 because of a previous error, which was discovered after the preliminary version of the article was posted online. The byline that had read “Ahmed K. Emara, MD1*, Ignacio Pasqualini, MD1*, Alison K. Klika, MS1, Melissa N. Orr, BS1, Pedro J. Rullán, MD1, Nicolas S. Piuzzi, MD1, and the Cleveland Clinic Arthroplasty Group†” now reads “Ahmed K. Emara, MD1*, Ignacio Pasqualini, MD1*, Yuxuan Jin, MS1, Alison K. Klika, MS1, Melissa N. Orr, BS1, Pedro J. Rullán, MD1, Nicolas S. Piuzzi, MD1, and the Cleveland Clinic Arthroplasty Group†”.

Background:
Literature-reported minimal clinically important difference (MCID) and patient acceptable symptom state (PASS) thresholds for patient-reported outcome measures demonstrate marked variability. The purpose of this study was to determine the minimal detectable change (MDC), MCID, and PASS thresholds for the Knee injury and Osteoarthritis Outcome Score (KOOS) Pain subdomain, Physical Function Short Form (PS), and Joint Replacement (JR) among patients with osteoarthritis (OA) who underwent primary total knee arthroplasty (TKA).

Methods:
A prospective cohort of 6,778 patients who underwent primary TKA was analyzed. Overall, 1-year follow-up was completed by 5,316 patients for the KOOS Pain, 5,018 patients for the KOOS PS, and 4,033 patients for the KOOS JR. A total of 5,186 patients had an OA diagnosis; this group had an average age of 67.0 years and was 59.9% female and 80.4% White. Diagnosis-specific MDCs and MCIDs were estimated with use of a distribution-based approach. PASS values were estimated with use of an anchor-based approach, which corresponded to a response to a satisfaction question at 1 year postoperatively.

Results:
The MCID thresholds for the OA group were 7.9 for the KOOS Pain, 8.0 for the KOOS PS, and 6.7 for the KOOS JR. A high percentage of patients achieved the MCID threshold for each outcome measure (KOOS Pain, 95%; KOOS PS, 88%; and KOOS JR, 94%). The MDC 80% to 95% confidence intervals ranged from 9.1 to 14.0 for the KOOS Pain, 9.2 to 14.1 for the KOOS PS, and 7.7 to 11.8 for the KOOS JR. The PASS thresholds for the OA group were 77.7 for the KOOS Pain (achieved by 73% of patients), 70.3 for the KOOS PS (achieved by 68% of patients), and 70.7 for the KOOS JR (achieved by 70% of patients).

Conclusions:
The present study provided useful MCID, MDC, and PASS thresholds for the KOOS Pain, PS, and JR for patients with OA. The diagnosis-specific metrics established herein can serve as benchmarks for clinically meaningful postoperative improvement. Future research and quality assessments should utilize these OA-specific thresholds when evaluating outcomes following TKA. Doing so will enable more accurate determinations of operative success and improvements in patient-centered care.

Level of Evidence:
Prognostic Level II. See Instructions for Authors for a complete description of levels of evidence.