Cross-cultural Adaptation and Validation of the KOOS, JR Questionnaire for Assessing Knee Osteoarthritis in Spanish-speaking Patients

Abstract Background The Knee Injury and Osteoarthritis Outcome Score, Joint Replacement (KOOS, JR), a validated short form (7 questions) from the original KOOS score (42 questions), has demonstrated higher response rate among other patient-reported outcome measures (PROMs) in patients with knee osteoarthritis (OA). However, there is no validated Spanish version. The present study aims to translate, adapt, and validate a Spanish version of the KOOS, JR, including a reliability and validity analysis. Methods Prospective validation study following the six stages of the "Guidelines for the Process of Cross-Cultural Adaptation of Self-Report Measures". Stage I: Translation from the original English version to Spanish by two native Spanish speakers. Stage II: Synthesis with linguistic and legibility test. Stage III: Back translation by two blinded native English speakers. Stage IV: Expert committee review of the final Spanish version. Stage V: Pretesting in 10 volunteers with similar demographic characteristics as the target study population. Stage VI: Approval by the expert committee and the original developer. Psychometric testing was conducted in a new group of participants: patients with knee OA. Subjects answered the Spanish KOOS, JR (S-KOOS, JR), and a validated Spanish Oxford Knee Score (S-OKS). Re-test were conducted at 10 days. Acceptability, floor and ceiling effect, internal consistency (Cronbach’s α), reproducibility (mixed-effect model coefficient [MEMC]), and construct validity (Spearman's correlation; p = 0.05) were assessed. Results 41 patients (mean age: 65.6 ± 5.39; 48.8% female) participated in the study. All patients (100%) answered both scores during the first assessment and thirty-eight (92.7%) during the second assessment. All PROMs were answered completely (100%). The S-KOOS, JR resulted in 100% acceptability when answered. There were no ceiling or floor effects detected. The Cronbach's α for the S-KOOS, JR was 0.927, and its MEMC was 0.852 (CI 95%: 0.636–1.078). The Spearman's correlation between the S-KOOS, JR and the S-OKS was 0.711 (CI: 0.345–0.608; p < 0.001) and 0.870 (IC: 0.444–0.651; p < 0.001) for the first and second assessments, respectively. Conclusion The S-KOOS, JR has very high internal consistency and reproducibility, with a high correlation with the S-OKS; it is a reliable and valid instrument for characterizing Spanish-speaking patients suffering from knee OA.