Comparative Study Evaluating the Mobility of Transtibial Amputee Patients Using the PRO-FLEX PIVOT® Foot Versus a Class III Energy Storing and Returning (ESAR) Prosthetic Foot.

Inclusion Criteria: Adult patient (over 18 years of age) * Unilateral tibial amputee and fitted for at least 6 months with a class III ESAR foot. * Regularly using (more than 8 hours/day) a class III ESAR foot * Functional class (CNEDiMTS indication)1 * Insured person. * Able to answer questionnaires. * Providing informed and written consent to participate in the study. * Having a normalized PLUS-M/FC 12 score less than 50 for vascular amputee and 55 for traumatic amputee and other causes of amputation. * Experiencing no discomfort related to the socket indicated by a score ≥ 6 on the numerical scale from 0 to 10 (Socket Comfort Score) Exclusion Criteria: * Bilateral lower limb amputation * Femoral amputation * Wearing a temporary prosthesis * Change of socket or suspension system planned during the study. * Change of any functional component as torsion or choc adapter * Significant change in the patient's routine activities expected during the study. * Progressive associated pathology that may prevent patient follow-up. * Associated pathology that may limit the patient's mobility (e.g. disarticulation of the knee, knee pain... ) * No osteointegration patients * Lack of consent * Adult subject to enhanced protection, deprived of liberty by judicial or administrative decision, hospitalized without consent or admitted to a health or social institution for purposes other than research. * Person not affiliated with or a beneficiary of a health insurance plan. * Patient unable to understand the study instructions