How Do Patients Above Patient Acceptable Symptom State Pre-Operatively Recover Following Total Knee Arthroplasty?

Background/Objectives: Patient acceptable symptom state (PASS) thresholds have been used as a marker of good functional outcome following total knee arthroplasty (TKA) but have not been applied to pre-operative subjective function. This study aimed to compare the outcomes of patients above and below PASS thresholds prior to TKA. Methods: A secondary analysis of a multicenter prospective observational study was used, including 1182 patients prescribed a smartphone-based care management platform following TKA with pre-operative and 1-year KOOS JR scores available. Patient demographics, pain, satisfaction, and KOOS JR were compared between those above and below PASS pre-operatively by student t-test. Logistic regression was used to quantify the odds of decline or no improvement at 1 year. Results: In this cohort, 191 (16.2%) KOOS JR scores were above PASS thresholds prior to TKA. Those above PASS reported lower pain pre-operatively (3.7 ± 1.9 vs. 6.0 ± 1.9, p < 0.0001) and less pain reduction at 90 days (−1.4 ± 2.5 vs. −3.2 ± 2.6, p < 0.0001). Patients above PASS also demonstrated higher KSS satisfaction scores pre-operatively (20.7 ± 7.9 vs. 12.1 ± 6.7, p < 0.0001) with less improvement (9.9 ± 10.6 vs. 16.5 ± 11.2, p < 0.0001) at 90 days. In logistic regression, those above PASS pre-operatively were 5.1 times more likely to report a decline or no improvement in KOOS JR at 1 year (5.10 95% CI 2.73–9.53, p < 0.0001). Conclusions: Patients above previously defined PASS thresholds who presented for TKA appreciated less improvement in pain and satisfaction and were more likely to experience functional decline or no improvement in KOOS JR post-operatively. The application of PASS thresholds pre-operatively may be useful for patient selection or guidance of patient expectations.