Chronic Venous Insufficiency and Balneotherapy

Inclusion Criteria: * Primary or post-thrombotic CVD with confirmed diagnosis by by duplex ultrasound examination (last available exam); * With CVI classified as C4a, C4b, or C5) * Available for balneotherapy program within the 2 next months * With health insurance affiliation. Exclusion Criteria: * Active venous thrombosis, recent or ongoing erysipelas, peripheral arterial pathology (ankle brachial index \< 0.70). * Walking difficulty * Neurologic diseases of the lower limbs * Presenting or likely to present a contraindication to thermal treatments, with planned surgery; * Having already benefited from a thermal treatment whatever the indication during the last 6 months * Chronic infectious disease, cancer, heart, kidney or liver failure; * Pregnant, breastfeeding women or women planning a pregnancy within the year; * Persons deprived of their liberty or subject to psychiatric care or subject to a measure of legal protection or unable to express their consent; * Patient likely to not respect the protocol or not to be able to attend the visits, particularly given the study follow-up; * Living at more than 30 minutes from the thermal site or who cannot be accommodated less than 30 minutes from the thermal site; * Already included in a clinical trial or in the exclusion period of a clinical trial.