 The main objective of the study is the evaluation of the outcomes following treatment for TMC OA using a set of variables covering all OMERACT categories as well as the dimensions of the International Classification of Functioning, Disability and Health ICF. Secondary aims are the analysis of the determinants of patient satisfaction with the treatment result, the evaluation of the psychometric properties of the Michigan Hand Outcomes Questionnaire MHQ, which has not yet been established in TMC OA patients, as well as the economic impact associated with TMC OA. 