Background: Patellofemoral pain is a very common complaint in orthopedic sports medicine clinics. Disease-specific patient-reported outcome measures (PROMs) are useful for research and clinical practice; thus, it is important to have validated translations available for new PROMs. This study aims to translate and validate the Spanish version of the patellofemoral pain and osteoarthritis subscale of the knee injury and osteoarthritis outcome score (KOOS-PF).
Methods: The KOOS-PF was translated and culturally adapted to Spanish following current guidelines, which included translation, back-translation, conciliation and pilot studies. Patients with a diagnosis of patellofemoral pain and/or osteoarthritis from one medical center were invited to participate and complete the questionnaire. The evaluation of the score included internal consistency (Cronbach´s alpha), floor and ceiling effects, measurement error, minimal detectable change and minimal important change. For test-retest reliability, the intraclass correlation coefficient (ICC) was used, and for responsiveness, the global rating of change (GROC) scale was measured one month later.
Results: Sixty patients with patellofemoral pain and/or osteoarthritis were included in the study. The Spanish version showed very good internal consistency (Cronbach’s alpha: 0.93) and test-retest reliability (intraclass correlation coefficient: 0.82). Responsiveness was confirmed, with the KOOS-PF demonstrating a strong correlation with the GROC score (r 0.64). The minimal detectable change was 11.1 points, the minimal important change was 17.2 points, and there were no floor or ceiling effects for the score.
Conclusions: The Spanish version of the KOOS-PF demonstrated very good measurement properties, including internal consistency, reliability and responsiveness. The KOOS-PF can be used in Spanish-speaking patients for clinical and research purposes in patellofemoral pain and osteoarthritis.
Trial registration: Fundación Valle del Lili, Biomedical Research Ethical Committee: No. 01438.