Objective: To evaluate the psychometric properties of the French KOOS physical function (KOOS-PS) and HOOS physical function (HOOS-PS), specifically its feasibility, reliability, construct validity, and responsiveness.
Methods: Consecutive outpatients consulting for primary knee or hip osteoarthritis (OA) in a rheumatology department were included. During the initial assessment, patients were asked to complete the Knee injury and Osteoarthritis Outcome Score (KOOS) or Hip disability and Osteoarthritis Outcome Score (HOOS) questionnaire and the OsteoArthritis Knee and Hip Quality Of Life questionnaire (OAKHQOL). The patients were given a second KOOS or HOOS questionnaire to complete and return by mail 2 weeks later. Feasibility was assessed by calculating the percentage of missing items and the floor and ceiling effects. Test-retest reliability was evaluated using the intra-class correlation coefficient (ICC). Convergent and divergent construct validity was determined by comparing the results of the KOOS-PS or HOOS-PS and OAKHQOL questionnaires using Spearman's rank test. Responsiveness was evaluated using data obtained in other hip or knee OA patients prior to and 1 month after intra-articular hyaluronic acid injection, using standardized response mean (SRM) and effect-size (ES).
Results: Eighty-seven patients with knee OA and 50 hip OA patients were included. The KOOS-PS and HOOS-PS scores were obtained for all patients as there were no missing items. Neither a floor nor a ceiling effect was observed. The ICC of KOOS-PS and HOOS-PS was 0.861 (0.763-0.921) and 0.859 (0.725-0.929), respectively. A strong or moderate correlation was observed, as expected, between KOOS-PS, HOOS-PS, and the OAKHQOL physical activities, pain, and mental health domains. A weak correlation was observed, as expected, between KOOS-PS, HOOS-PS, and the other OAKHQOL domains, except for a moderate correlation between the KOOS-PS and social functioning. The responsiveness was demonstrated with SRM and ES of 0.80 and 0.51 (KOOS-PS), 1.10 and 0.62 (HOOS-PS), respectively.
Conclusion: The French versions of KOOS-PS and HOOS-PS are reliable, valid, and responsive questionnaires for capturing functional disability in people with knee and hip OA.