What Outcome Metrics Do the Various Knee Rating Systems for Assessment of Outcomes Following Total Knee Arthroplasty Measure? A Systematic Review of Literature.

Multiple scoring systems have been developed for the assessment of outcomes following total knee arthroplasty. However, few studies have comprehensively evaluated each scoring system to analyze the various outcome variables and their individual weightings toward generations of the final score. A systematic search of four electronic databases were performed from January 1960 to August, 2013 to identify studies that reported on knee scores and to sub-categorize the outcomes measured based on subjective, objective, rehabilitative, and quality of life outcomes. We also evaluated the outcome metrics that each of these systems measured to identify the relative impact of these variables toward the final score. We identified 45 different outcome metrics in 46 rating scales. Pain (80%), stiffness (13%), and swelling (13%) were the three most common subjective outcomes measured in the scoring systems, while measurements of range-of-motion (57%), flexion contracture (39%), and coronal plane deformity (35%) were the most often reported objective outcome variables. Of all the variables measured, we found that pain (mean weighted score, 26 points; range, 0 to 50 points), range-of-motion (mean weighted score, 11 points; range, 0 to 50 points), distance walked (mean weighted score, 7 points; range, 0 to 30 points), ability to climb stairs (mean weighted score, 6 points; range, 0 to 20 points), ability to rise from sitting position (mean weighted score, 4 points; range, 0 to 20 points), and presence of a flexion contracture (mean weighted score, 4 points, range, 0 to 20 points) had the greatest impact on the final score standardized to 100 points. Currently, few rating scales exist that assess all aspects of functional, rehabilitative, and quality of life outcomes including patient satisfaction within the realms of a single scoring system. Further research is needed to determine the optimal combination and weightings of the individual outcomes metrics to better evaluate overall outcomes following total knee arthroplasty and to develop a more comprehensive scoring system.