Cross-cultural adaptation of the VISA-P questionnaire for Greek-speaking patients with patellar tendinopathy.

Objectives: To cross-culturally adapt the VISA-P questionnaire for Greek-speaking patients and evaluate its psychometric properties.
Background: The VISA-P was developed in the English language to evaluate patients with patellar tendinopathy. The validity and use of self-administered questionnaires in different language and cultural populations require a specific procedure in order to maintain their content validity.
Methods: The VISA-P questionnaire was translated and cross-culturally adapted according to specific guidelines. The validity and reliability were tested in 61 healthy recreational athletes, 64 athletes at risk from different sports, 32 patellar tendinopathy patients and 30 patients with other knee injuries. Participants completed the questionnaire at baseline and after 15-17 days.
Results: The questionnaire's face and content validity were judged as good by the expert committee, and the participants. Concurrent validity was almost perfect (ρ=-0.839, p<0.001). Also, factorial validity testing revealed a two-factor solution, which explained 85.6% of the total variance. A one-factor solution explained 80.8% of the variance when the other knee injury group was excluded. Known group validity was demonstrated by significant differences between patients compared with the asymptomatic groups (p<0.001). The VISA-P-GR exhibited very good test-retest reliability (ICC=0.818, p<0.001; 95% CI 0.758 to 0.864) and internal consistency since Cronbach's α analysis ranged from α=0.785 to 0.784 following a 15-17 days interval.
Conclusions: The translated VISA-P-GR is a valid and reliable questionnaire and its psychometric properties are comparable with the original and adapted versions.
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