Improvement After Total Knee Arthroplasty to a Knee Injury and Osteoarthritis Outcome Score for Joint Replacement...

The Center for Medicare and Medicaid is introducing the merit-based incentive payment system, requiring outcome reporting. A potential measure is the proportion of patients who have a postoperative Knee injury and Osteoarthritis Outcome Score for Joint Replacement (KOOS Jr.) score of 71. This study aimed to determine the percentage of patients who achieved this threshold at one year following primary total knee arthroplasty, the various predictors of this outcome, and the proportion who achieved substantial clinical benefit (SCB).

A database of primary total knee arthroplasty cases performed at an academic institution from 2017 to 2023 was queried. Demographic and clinical variables such as age, sex, body mass index, ethnicity, other joint pain, low back pain (Oswestry Questionnaire), and Veterans RAND 12-Item Health Survey scores were tabulated. The KOOS Jr. scores were recorded at the preoperative and 1-year postoperative visit. Patients who had KOOS Jr. improvement of at least 20 points achieved SCB. Univariate analyses were performed with Chi-square and t-tests, followed by multivariate regressions.

The cohort consisted of 3,217 patients, of whom 32.5% achieved a KOOS Jr. of at least 71. Of 2,572 patients who had both preoperative and postoperative KOOS Jr. scores, 1,580 (61.4%) achieved SCB, of whom 728 (46.1%) had a postoperative KOOS Jr. score of at least 71. After multivariate analyses, patients who were less likely to meet the cutoff exhibited lower preoperative KOOS Jr. scores (P = 0.003), a lower preoperative mental component score (P < 0.001), additional painful joints (P < 0.001), low back pain (P < 0.001), or were identified as African American (P = 0.003), Asian (P = 0.017), or Hispanic/Latino (P = 0.001).

Patients may achieve meaningful clinical benefit without achieving the KOOS Jr. threshold at 1-year postoperatively. This study informs outcome reporting as new payment models are adopted.