Translation, cross‐cultural validity and reliability of a Danish version of the Banff Patella Instability Instrument 2.0 (BPII 2.0)

Abstract Purpose This study aimed to translate and cross‐culturally validate a Danish version of the BPII 2.0, and assess its construct validity, internal consistency and test‐retest reliability in a Danish population of patients with patellar instability. Methods The BPII 2.0 was translated and cross‐culturally validated according to international guidelines, including 15 think‐aloud interviews in patients with patellar instability. Responses from 100 patients with patellar instability were accustomed to evaluating, construct validity, floor and ceiling effect, minimal detectable change, internal consistency and test‐retest reliability. Construct validity was assessed using Spearman Rho ( r ) comparing the BPII 2.0‐DK with the Kujala‐DK, the International Knee Documentation Committee (IKDC), the Victorian Institute of Sport Assessment‐Patella (VISA‐P) and the Tegner activity score (TAS). Structural validity was assessed using confirmatory factor analysis (CFA). Internal consistency reliability was evaluated using Cronbach's alpha. Test‐rest reliability was examined using Pearson's intraclass correlation coefficient (ICC) in 57 patients who completed the BPII 2.0 twice, with a one‐week interval. The study followed the COSMIN guidelines. Results Minor comprehensibility issues were corrected during translation, and patients found the BPII 2.0‐DK relevant and comprehensive. High positive correlations were found with the Kujala‐DK ( r = 0.73), IKDC ( r = 0.81) and VISA‐P ( r = 0.67), whereas only a low correlation was found with the TAS ( r = 0.44). CFA demonstrated loadings ranging from 0.45 to 0.84. No ceiling or floor effects were observed, and a minimal detectable change of 15.3 points was found. Cronbach's alpha was 0.95, indicating excellent internal consistency, and ICC was 0.90 (95% CI: 0.86–0.94) for test‐retest reliability. Conclusion The BPII 2.0‐DK is a relevant, comprehensible, and comprehensive tool for patients with patellar instability. There was a high positive correlation between BPII 2.0 and Kujala‐DK, IKDC and VISA‐P. Furthermore, excellent internal consistency reliability and high test‐retest reliability were found. Level of Evidence Level III.