The 10-item NDI was translated into German and administered to 558 patients with chronic unspecific
neck pain (Mean age 49.9 ± 11.4 years, 76% female). The factor structure and reliability of the NDI were assessed
using factor analysis, Cronbach’s alpha, split-half reliability (Spearman-Brown coefficient), and intra-class correlation
(ICC2,1). To determine convergent validity, pain intensity (visual analog scale; VAS), pain on movement (VAS), and
quality of life (Short Form 36 Health Survey Questionnaire; SF-36) were correlated with the NDI. Correlation with
range of motion and sensitivity to change were also assessed in a subsample of 49 patients.