JOA - 2026-03-29 - Journal Article
Minimal Clinically Importance Difference and Substantial Clinical Benefit in Total Knee Arthroplasty: Delayed Achievers and Maintaining Improvement.
Nin DZ, Chen YW, Chen YH, Talmo CT, Hollenbeck BL, Travers H, Kuznetsov M, Niu R, Chang DC, Smith EL
Topics
Key Takeaway
72.4% of TKA patients achieved MCID on KOOS JR by 12 months, but 9.9% were delayed achievers (by 24 months) and 11.0% failed to maintain early MCID gains.
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Summary
This registry-based observational study identified predictors of delayed MCID/SCB achievement and failure to maintain early gains on KOOS JR following primary TKA. Among 664 patients, 63.1% achieved early SCB by 12 months and 13.0% were delayed achievers by 24 months; 8.4% failed to maintain early SCB. Delayed MCID achievers had lower baseline stiffness scores (52.3 vs 61.3, p=0.005), but multivariate analysis identified no independent patient-level predictors of delayed achievement or failure to maintain improvement.
Key Limitation
Multivariate analysis failed to identify actionable predictors of delayed achievement or non-maintenance, leaving clinicians without a validated tool to prospectively identify at-risk patients.
Original Abstract
INTRODUCTION
Improvement in Knee injury Osteoarthritis Outcome Survey, Joint Replacement (KOOS, JR) scores is commonly used as a marker of patient satisfaction following total knee arthroplasty (TKA). The purpose of this study was to determine predictors of patients who had delayed achievement of satisfied KOOS, JR scores following TKA and those who did not maintain their score despite achieving an early high score.
METHODS
We conducted an observational cohort study using our institutional registry comprising patient-reported outcomes collected pre- and postoperatively at 3-, 6-, 12-, and 24-month intervals following TKA. The primary outcome was the achievement of minimal clinically important difference (MCID) and substantial clinical benefit (SCB) in KOOS, JR scores at 24 months. Multivariate logistic regressions were performed to determine the likelihood of delayed achievement of MCID/SCB and not maintaining early achievement of MCID/SCB.
RESULTS
Among the 664 patients included in the study, 72.4% of patients achieved early MCID (i.e., 12 months), and 9.9% had a delayed achievement (i.e., 24 months). With the SCB benchmark, 63.1% of patients achieved early SCB and 13.0% achieved delayed SCB. There were 11.0 and 8.4% of patients who did not maintain MCID and SCB after early achievement, respectively. Patients who had delayed MCID achievement had lower (P = 0.005) baseline stiffness scores (52.3 ± 20.0) compared to patients who did not achieve MCID (61.3 ± 21.4). Adjusted analyses did not identify significant predictors related to patient characteristics or baseline survey responses of the likelihood of delayed MCID/SCB achievement or maintenance of early MCID/SCB at 24 months.
CONCLUSIONS
The majority of patients achieve MCID or SCB within 12 months of TKA. Poorer preoperative knee health, especially related to stiffness, may be a driver of eventual achievement for patients who have unsatisfactory patient-reported outcome scores immediately after surgery.