Development and validation of a culturally relevant Japanese KOOS

The Knee Injury and Osteoarthritis Outcomes Survey (KOOS) has been translated into 50 languages worldwide. These translations have adhered to guidelines for cross cultural adaptation of health surveys. However, after release of the Japanese KOOS (JKOOS) we discovered the JKOOS was not fully culturally relevant to Japanese patients. Therefore, we undertook the development and validation of the JKOOS+.

We completed this project in 2 phases across 9 hospitals. In Phase 1, 187 surgically naïve patients with knee pain were asked about activities limited by their knee pain. An expert panel reconciled these activities against existing KOOS items to identify novel items. In Phase 2, 241 surgically naïve patients with knee pain were administered the Japanese Oxford Knee Survey, JKOOS, and these novel items. An iterative Rasch analysis was used to test item fit of these novel items within the KOOS Activities of Daily Living (ADL) domain and a potential new domain. Unidimensionality was assessed using principle component analysis. Internal consistency (Cronbach's alpha) and external validity (Spearman's Correlations) were assessed for Japanese ADL (J-ADL) and the novel domain.

Phase 1 identified 4 activities relevant to Japanese knee patients: sitting seiza, using a Japanese toilet, climbing hills, and getting on/off a bus/train. In Phase 2, climbing hills and bus/train were well fit in JADL. Seiza and using a Japanese toilet were not well fit in J-ADL, yet both require deep knee flexion so a knee flexion (KF) domain was constructed by considering all KOOS items that require knee flexion using an iterative Rasch model. An 8 item KF domain emerged. Both J-ADL and KF were deemed to be unidimensional with high internal consistency (Cronbach's alpha >0.92) and external validity (Spearman Correlations 0.723-0.929).

We have successfully developed and validated JKOOS+, a more culturally relevant knee survey for Japanese patients.