VALIDATION DATA

Cronbach's α was 0.96

ICC was 0.92 (CI 95%: 0.88-0.95) in the original validation for ankle inflammatory arthritis or osteoarthritis.

In patients with forefoot disorders, ICC was 0.92 (CI: 0.85–0.96). In patients with hindfoot or ankle disorders, ICC was 0.93 (CI: 0.88-0.96)

When the Swedish version of the questionnaire was created, the New Zealand total ankle questionnaire (Hosman et al. 2007) was translated into Swedish according to a standardized cross-cultural adaption procedure. The English questionnaire was forward translated into Swedish by 2 independent medically educated, native Swedish speakers. The Swedish version was then backward translated into English by a native English-speaking professional translator with no knowledge of the original version. The original English version was then compared with the backward-translated version, and if there was any discrepancy, these questions were made clearer by the 2 Swedish translators in a final Swedish version. This final version was then given to 10 patients with different hindfoot disabilities. They were asked to complete the questionnaire and were also asked if they understood all the questions. None of the volunteers reported any difficulty in completing the questionnaire.