Adjustments in 2011 KSS increase the clinical suitability.

The 2011 KSS is a valid clinical TKA questionnaire, but with a low completion rate (42%). Adjustments, focusing on optimizing scale features, are required to improve its clinical use. The low completion rates, non-optimal scale features, lacking rules or a combination of these factors where addressed, leading to the development of the adjusted 2011 KSS (2011 KSS-A). Four-hundred-ninety-nine primary TKA patients were addressed pre- and postoperative by mail. Clinimetric quality was evaluated. Seventy percent responded and 90% completed the scale. Internal consistency proved excellent with Cronbach's Alpha≥0.79 for all subscales. Strong correlations were found between the Functional Activity subscales and KOOS-PS (r=-0.63 to -0.87). All subscales improved significantly after intervention (r-range 14-33%, effect size 0.50-2.85). Postoperatively, ceiling effects were found in the subscales Symptoms (16%) and Walking & Standing (26%). Adjustments led to a shortened and simplified questionnaire while maintaining its clinimetric quality.