RESUMO
PURPOSE: The present study aims to translate, adapt and validate a Spanish version of the Knee Injury and Osteoarthritis Outcome Score, Joint Replacement (KOOS, JR), including a reliability and validity analysis in patients with knee osteoarthritis (OA). METHODS: This study conducted a prospective validation study following the six stages of the "Guidelines for the Process of Cross-Cultural Adaptation of Self-Report Measures". Psychometric testing was conducted in patients with knee osteoarthritis. Subjects answered the Spanish KOOS, JR (S-KOOS, JR) and a validated Spanish Oxford Knee Score (S-OKS). Retest was 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: Forty-one 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 38 (92.7%) during the second assessment. All patient-reported outcomes measures 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 (CI 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 characterising Spanish-speaking patients suffering from knee OA. LEVEL OF EVIDENCE: IV.