Cross-cultural Validation of the Norwegian Version of the Banff Patellofemoral Instability Instrument 2.0.

Background: The Banff Patellofemoral Instability Instrument (BPII) 2.0 is a disease-specific quality of life questionnaire for patients with patellofemoral instability. While good psychometric properties have been demonstrated, the data lack cross-cultural validity, construct validity, and an established measurement error.

Purpose: To (1) translate and cross-culturally adapt the BPII 2.0 to the Norwegian version (BPII 2.0-No) and (2) examine the psychometric properties of the Norwegian version.

Study Design: Cohort study (diagnosis); Level of evidence, 3.

Methods: The BPII 2.0 was translated according to international guidelines. A cohort of 100 patients surgically treated for recurrent patellofemoral instability completed the BPII 2.0-No, related outcome measures (Norwich Patellar Instability Score, International Knee Documentation Committee Subjective Knee Form 2000, Knee injury and Osteoarthritis Outcome Score, and Tampa Scale of Kinesiophobia), and functional tests (Y-Balance Test-Lower Quarter, single-leg hop tests, and knee extension strength) before and/or 6 months after surgery. We evaluated the face and content validity, internal consistency (Cronbach α), test-retest reliability (intraclass correlation coefficient [ICC]), measurement error (SEM and smallest detectable change at the individual [SDC] and group levels [SDC]). Construct validity was assessed by testing 9 hypotheses on the correlation between the BPII 2.0-No and the outcome measures/functional tests (Pearson ).

Results: The BPII 2.0-No had good face and content validity. Internal consistency was excellent (α = .95), and no floor or ceiling effects were found. Test-retest reliability was high (ICC = 0.87; 95% CI, 0.77-0.93), and measurement error was low (SEM = 7.1). The SDC was 19.7 points and the SDC was 2.8 points. Eight of the 9 hypotheses regarding construct validity were confirmed.

Conclusion: The BPII 2.0-No was found to be valid and reliable. This study adds further knowledge on the measurement properties of the BPII 2.0 that can be used internationally.