Knee injury and Osteoarthritis Outcome Score (KOOS); reliability and validity in competitive athletes after anterior cruciate ligament reconstruction

Objective: To validate the Knee injury and Osteoarthritis Outcome Score (KOOS) for the assessment of competitive athletes with higher level sports activities after anterior cruciate ligament (ACL) reconstruction. Methods and Measures: Fifty-seven athletes (39 males and 18 females; age, 25.6 +/- 3.4 years; height, 179.6 +/- 7.4 cm; weight, 77.6 +/- 9.8 kg) after ACL reconstruction were asked to complete the Persian KOOS and Short Form-36 (SF-36) questionnaires in the test session. To evaluate test-retest reliability, all participants filled out the KOOS and SF-36, 6-8 days after the first visit. The properties of the KOOS in terms of reliability [Intraclass Correlation Coefficient (ICC)], internal consistency (Cronbach's alpha), dimensionality (item-scale correlation) and construct validity (Spearman's rank correlation) were evaluated. Results: No floor or ceiling effect was observed. The ICCs (S.E.M.s) of the KOOS subscales were: Pain 0.93 (2.2), Symptoms 0.85 (3.1), Activities of Daily Living 0.91 (2.9), Function in Sport and Recreation 0.75 (2.1) and Knee-related Quality of Life 0.89 (2.6). The Cronbach's alphas of the KOOS subscales were: Pain 0.91, Symptoms 0.75, Activities of Daily Living 0.96, Function in Sport and Recreation 0.86 and Knee-related Quality of Life 0.74. Spearman's rank correlations between the subscales of the KOOS and representative subscales of the SF-36 ranged from 0.40 to 0.79. Conclusion: This study illustrates the validity and reliability of the KOOS in measuring the functional status and quality of life of athletes after ACL reconstruction. This study further validates the use of the KOOS in highly competitive athletes in research on knee injuries. (C) 2011 Osteoarthritis Research Society International. Published by Elsevier Ltd. All rights reserved.