Responsiveness of the International Knee Documentation Committee Subjective Knee Form

Abstract

Background and Purpose: The International Knee Documentation Committee Subjective Knee Form was developed to measure change in symptoms, function, and sports activity in patients treated for a variety of knee conditions. Although previous research has demonstrated reliability and validity of the form, its responsiveness has not been evaluated. The purpose of this study was to determine responsiveness of the International Knee Documentation Committee Subjective Knee Form. Study Design: Cohort study (diagnosis); Level of evidence, 1. Methods: Patients who participated in the original validation study for the International Knee Documentation Committee Subjective Knee Form completed the form and a 7-level global rating of change scale that ranged from greatly worse to greatly better after a mean of 1.6 years (range, 0.5-2.3 years). Analyses included calculation of the standardized response mean and mean change in International Knee Documentation Committee Subjective Knee Form score compared to the patient's perception of change on the global rating of change scale. In addition, a receiver operating characteristic curve was plotted to determine the change in score that best distinguished patients who improved from those who did not. Results: The overall standardized response mean was 0.94, which is considered large. With the exception of those who were slightly worse or unchanged, the mean change in the International Knee Documentation Committee Subjective Knee Form score compared to the patients’ perceived global ratings of change was as expected (greatly worse,–15.1; somewhat worse,–8.4; slightly worse, 20.6; no change, 10.7; slightly better, 5.9; somewhat better, 18.1; greatly better, 38.7). The receiver operating characteristic curve analysis revealed that a change score of 11.5 points had the highest sensitivity, and a change score of 20.5 points had the highest specificity to distinguish between those who were or were not improved. Conclusion: The International Knee Documentation Committee Subjective Knee Form is a responsive measure of symptoms, function, and sports activity for patients with a variety of knee conditions.