Content validity of the International Classification of Functioning, Disability and Health core set for knee dysfunction: a Delphi study

Objective To assess the content validity of the preliminary core set for knee dysfunction based on the opinion of experts. Design A panel of 180 experts in knee disorders or on the use of the International Classification of Functioning, Disability, and Health for musculoskeletal conditions was invited for this Delphi study. The experts gave their opinion on whether to include the categories of the preliminary core set for knee dysfunction in a more comprehensive core set, using a six-item Likert scale. Kappa coefficient was used to analyze the agreement between the experts, and a consensus of 75% among responses was considered acceptable. Results Nineteen experts participated in all rounds. Of the 24 categories from the preliminary core set for knee dysfunction, 15 remained in the comprehensive core set and one category was further detailed into three new categories. Seven new categories were included. Thus, the comprehensive core set for knee dysfunction was composed of 25 categories with an agreement of 81.5% among responses and a Kappa value of 0.63. Conclusion After validation by experts, the comprehensive core set for knee dysfunction was composed of 25 categories that can be used to assess the functioning of patients with knee dysfunction.