Validation of a Persian-version of Knee injury and Osteoarthritis Outcome Score (KOOS) in Iranians with knee injuries.

OBJECTIVE: To adapt culturally and validate Persian-version of the Knee injury and Osteoarthritis Outcome Score (KOOS) in a sample of Iranians with knee injuries.

METHODS: Cultural adaptation included providing of forward and backward translations, quality rating and pilot testing. A sample of 147 patients with anterior cruciate ligament (ACL), meniscus and combined (ACL and meniscus) injuries was asked to complete two questionnaires including the KOOS and Short-Form 36 Health Survey (SF-36). The KOOS was readministered to 54 patients 6-8 days after the first visit. Test-retest reliability and internal consistency were assessed, using Intraclass Correlation Coefficient (ICC) and Cronbach's alpha, respectively. Dimensionality was assessed, using item-scale correlation after correction for overlap and construct validity, using a priori hypothesized correlations with the SF-36.

RESULTS: All patients found the Persian-version of the KOOS to be clear and unambiguous in pilot testing. Minimum ICC level of 0.70 was exceeded by all subscales with the exception of Sport and Recreation (Sport/Rec) subscale. Minimum Cronbach's alpha level of 0.70 was exceeded by all subscales with the exception of Symptoms and Knee-related Quality of Life (QoL). Minimum Spearman correlation coefficient of 0.40 for each item-scale was exceeded by 34 items. All priori hypotheses were supported by the presence of higher correlations between similar constructs than between dissimilar constructs of the KOOS and SF-36.

CONCLUSION: The Persian-version of the KOOS is a culturally-adapted, reliable and valid outcome measure to be used in Iranian patients with knee injuries, with its psychometric properties in agreement with the original versions.