Minimal clinically important difference of commonly used patient-reported outcome measures in total knee arthroplasty: review of terminologies, methods and proposed values

The aim of this article was to highlight various terminologies and methods of calculation of minimal clinically important difference (MCID) and summarize MCID values of frequently used patient-reported outcome measures (PROMs) evaluating total knee arthroplasty (TKA). PubMed and EMBASE databases were searched through May 2019. Of 71 articles identified, 18 articles matched and underwent a comprehensive analysis for terminologies used to indicate clinical significance, method of calculation, and reported MCID values. MCID was the most common terminology (67% studies) and anchor-based methods were most commonly employed (67% studies) to calculate it. The analytical methods used to calculate and the estimated values of MCID for clinical use are highly variable. MCID values reported for WOMAC scores are 20.5 to 36.0, 17.6 to 33.0 and 12.9 to 25.0 for pain, function and stiffness sub-scales, respectively, and 4.7 to 10.0 for OKS. There was lack of standardization in the methodology employed to calculate MCID in the available studies. MCID values reported in this review could be used for patients undergoing TKA, although caution is advised in their interpretation and application.