Establishing Diagnosis-Specific Measures of Clinical Meaningfulness for the Knee Injury and Osteoarthritis Outcome Score in Aseptic Revision Total Knee Arthroplasty

Background: Revision total knee arthroplasty (rTKA) projections indicate substantial growth. Although patient-reported outcome measures are valuable for assessing rTKA outcomes, interpretation of clinical relevance remains challenging. This study aimed to determine diagnosis-specific thresholds for minimal clinically important difference (MCID), patient-acceptable symptom state (PASS), and substantial clinical benefit (SCB) for Knee Injury and Osteoarthritis Outcome Score (KOOS) scores in aseptic rTKA. Methods: A prospective cohort of 752 patients who underwent aseptic rTKA between 2016 and 2022 was analyzed. Patients were stratified by the following preoperative diagnosis: aseptic loosening (n = 313), implant failure (n = 93), instability (n = 320), and periprosthetic fracture (n = 26). The KOOS-Pain, KOOS-Physical Function Short Form (PS), and KOOS-Joint Replacement (JR) scores were collected preoperatively and at a 1-year follow-up. The MCID was calculated using distribution-based methods; PASS and SCB were determined using anchor-based approaches. Results: The MCID thresholds ranged from 8.5 to 11.0 for KOOS-Pain, 8.8 to 12.0 for KOOS-PS, and 7.7 to 9.8 for KOOS-JR. The PASS thresholds varied from 62.5 to 80.6 for KOOS-Pain, 58.0 to 63.0 for KOOS-PS, and 59.4 to 76.3 for KOOS-JR. The SCB thresholds spanned 30.6 to 44.5 for KOOS-Pain, 13.3 to 26.2 for KOOS-PS, and 11.8 to 42.0 for KOOS-JR. Periprosthetic fracture consistently showed the highest achievement rates across all measures (MCID: 76 to 92%, PASS: 44 to 77%, SCB: 41 to 62%), whereas instability demonstrated the lowest (MCID: 64 to 75%, PASS: 44 to 53%, SCB: 15 to 33%). Conclusions: This study established diagnosis-specific thresholds for MCID, PASS, and SCB across multiple KOOS measures in aseptic rTKA. The findings reveal notable variability in these thresholds depending on preoperative diagnosis, highlighting the importance of individualized assessment and expectation management in rTKA, rather than applying uniform thresholds across all revision indications.