JOA - 2026-06-12 - Journal Article
Differences Between Inpatient and Outpatient Medicare Total Knee Arthroplasty: Substantial Clinical Benefit Thresholds on Knee Injury and Osteoarthritis Outcome Score for Joint Replacement.
Patel SV, Pasqualini I, Khan ST, Elmenawi KA, Zhang C, Piuzzi NS, Cleveland Clinic Adult Reconstruction Research (CCARR) Group
Topics
Key Takeaway
Medicare TKA inpatients require a KOOS-JR improvement of 29.3 points to achieve substantial clinical benefit, nearly 8 points higher than the 21.5-point threshold derived for outpatients.
Summary Depth
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Summary
This study asked whether the CMS PRO-PM universal KOOS-JR SCB threshold of ≥20 points equitably captures meaningful improvement across inpatient and outpatient TKA settings in Medicare beneficiaries ≥65 years. Using anchor-based ROC analysis with the Veterans RAND 12-Item global physical health transition question, setting-specific thresholds were derived from a 2016–2022 dataset. The inpatient SCB threshold was 29.3 points (AUC 0.705) vs. 21.5 points for outpatients (AUC 0.706), with 64.3% and 65.6% of each cohort achieving SCB by their respective thresholds.
Key Limitation
The study does not report postoperative follow-up timing uniformly, and without controlling for baseline KOOS-JR scores—which are systematically lower in inpatients—it is unclear whether the threshold difference reflects true responsiveness differences or is entirely attributable to floor effects from worse preoperative status.
Original Abstract
BACKGROUND
The Centers for Medicare & Medicaid Services (CMS) Patient-Reported Outcome-Based Performance Measure (PRO-PM) mandates collection of patient-reported outcome measures (PROMs) after total knee arthroplasty (TKA) and defines success as achieving substantial clinical benefit (SCB) on the Knee injury and Osteoarthritis Outcome Score for Joint Replacement (KOOS-JR) of ≥ 20 points. As TKA increasingly shifts to outpatient care and patient complexity varies by care setting, a single universal threshold may misclassify improvement. This study estimated specific KOOS-JR SCB thresholds in separate Medicare inpatient and outpatient cohorts and compared the performance of these thresholds between settings.
METHODS
A retrospective analysis of prospectively collected data on 7,926 Medicare beneficiaries ≥ 65 years who underwent primary elective TKA from 2016 to 2022 was performed. Patients were stratified by care setting into inpatient (n = 2,812) and outpatient (n = 5,114) cohorts. The SCB thresholds on KOOS-JR were derived using an anchor-based approach with the Veterans RAND 12-Item, "Compared to one year ago, how would you rate your physical health now?" as the anchor. Receiver operating characteristic analysis with Youden's index identified setting-specific cut points.
RESULTS
The KOOS-JR SCB threshold for the inpatient Medicare cohort was 29.3 points (Youden's index 0.303 and area under the curve (AUC) 0.705). Using this threshold, 64.3% of inpatients achieved SCB. For outpatients, the SCB threshold was 21.5 points (Youden's index 0.317 and AUC 0.706). With this threshold, 65.6% of outpatients attained SCB.
CONCLUSIONS
Calculating separate inpatient and outpatient KOOS-JR SCB thresholds for Medicare TKA patients yielded notably different cut points, with the inpatient threshold being nearly eight points higher than the outpatient. This gap possibly reflects underlying differences in baseline status and comorbidity burden between care settings. Threshold interpretation adjusted for such patient factors rather than a single universal cut-point may support more equitable and fair performance evaluation.