Power and sample size calculation The required number of patients has been estimated based on qualities to assess. The reproducibility (test-retest) of the questionnaire is one of the main properties and assess the lower acceptable limit is .85. However, knowing that the reproducibility of the English version was .97, the investigators estimated that the French version would be at least .90. A sample of 10 patients would be sufficient to obtain a power of 99% with a reproducibility of .901,9. Regarding validity, the investigators wish to obtain a statistically significant correlation with the three selected tests. The investigators hypothesized that the lowest correlation between the AOS-Fr and the SF-36 questionnaire would provide the lowest correlation, because the SF-36 is not specific to ankle OA. By estimating an average correlation of .50, 30 patients are required to obtain a significant correlation with a power of 80% and p < .051,9.