Validity and comprehensibility of the International Knee Documentation Committee Subjective Knee Evaluation form in Children.

The International Knee Documentation Committee (IKDC) Subjective Knee Evaluation Form is a knee-specific measure developed for adults. Its usefulness in children is not established. This study describes how children interpret IKDC items, identifies sources of response errors, and provides suggestions for modification. Cognitive interviews were conducted in 30 children with a primary knee injury, purposefully sampled based on age and gender. Most children could not recall their injury date or symptoms 4 weeks after injury. All reported problems interpreting directions; half noted item timeframes were unclear and did not realize all questions pertained to their injured knee. Seventy percent read only the first half of a question, missing subtle differences between items. Children had difficulty comprehending the following concepts: strenuous/moderate activity, pivoting, locking, giving way, significant pain/swelling, and knee catching. Examples to describe activity levels either did not apply (e.g. housework) or were ranked differently by children. Younger children had difficulty using five-point responses. The two most difficult items were assessment of current and prior function. Children found the IKDC Subjective Knee Evaluation Form difficult to comprehend and to answer. Modifications to directions, item formatting, and definitions are needed to ensure comprehensibility and validity.