Comparison of Responsiveness of Patient-Reported Outcome Measures After Total Knee Arthroplasty.

Background: The aim of this study was to evaluate the responsiveness of different patient-reported outcome measures in patients with primary total knee arthroplasty (TKA).

Methods: In this prospective observational study, we assessed patients with TKA before the surgery, after 4 months, after 1 year, and after 2 years. Measures were the objective Knee Society Score (KSS) and the following patient-reported outcome measures: Knee injury and Osteoarthritis Outcome Score (KOOS), KOOS-12, Forgotten Joint Score (FJS-12), High-Activity Arthroplasty Score, and EQ-5D-3L. Responsiveness was determined by effect size (ES), standardized response mean (SRM), area under the receiver operating characteristics curve, floor and ceiling effects, and hypothesis testing.

Results: We analyzed data from 309 TKAs (272 patients, 56% female). The ES and SRM for the change in KSS, KOOS, KOOS-12, FJS-12, and EQ-5D-3L from baseline to each follow-up were large (>0.8). The largest responsiveness from baseline to follow-up was found for the KSS, KOOS/KOOS-12 quality of life, KOOS-12 summary, KOOS-12 pain, and FJS-12 (2.0 > ES <3.9, 1.4 > SRM <2.4). The area under the curve from baseline to each follow-up was ≥0.7 for KOOS, KOOS-12, and FJS-12 (range 0.71 to 0.95) and <0.7 for KSS and EQ-5D-3L (range 0.65 to 0.74). We found floor or ceiling effects in the KOOS, KOOS-12, and EQ-5D-3L, but not in the KSS, FJS-12, and High-Activity Arthroplasty Score.

Conclusions: Our study demonstrated that responsiveness differed between the various measures. The KOOS-12 and FJS-12 showed the greatest internal and external responsiveness, although ceiling effects occurred in the KOOS-12.