The Danish version of the anterior knee pain scale (Kujala-DK): translation, cross-cultural adaptation and psychometric evaluation in patients with patellar instability.

Abstract

The aim of this study was to translate and cross-culturally adapt the Kujala into Danish (Kujala-DK) and investigate its psychometric properties in Danish patients with patellar instability. Content validity was assessed through 22 think-aloud cognitive interviews involving 15 patellar instability patients, 5 with patellofemoral pain, and 2 healthcare professionals. Data from 100 patellar instability patients were analysed to assess construct validity, internal consistency, test-retest reliability, floor and ceiling effects and minimal detectable change. Structural validity was assessed using confirmatory factor analysis (CFA). Construct validity was evaluated <i>via</i> Spearman's Rho. Internal consistency was evaluated with Cronbach's alpha and test-retest reliability with ICC in 57 patients who completed the Kujala twice, 7 days apart. The methods followed established guidelines. Patients found Kujala-DK relevant, comprehensible, and comprehensive. Items 11 and 12 were rephrased. CFA supported a unidimensional factor structure, with loadings ranging from 0.25 to 0.86. High correlations with IKDC and VISA-P and moderate agreement with TAS were observed. Internal consistency (α = 0.87) and test-retest reliability (ICC = 0.94) were high. The minimum detectable change was 13.0 points. The Kujala-DK demonstrate adequate construct validity and reliability and is recommended for clinical and research use in Danish-speaking patellar instability patients.