Socket is key to provide comfort and function to lower limb amputees. A new socket, the sub-ischial socket, will be compared to "traditional" ischial containment sockets, based on comfort self-evaluation, and locomotor capacities.

Subjects wearing ischail containment sockets will be proposed to enter the research. They will be provided and fitted with a sub-ischial socket. Randomly, they will use one or the other socket for four weeks, then be tested : finctional test and questionnaires. After this testing session, they will use the other socket, and be re-tested accordingly.

Inclusion Criteria:

• can give informed consent
• aged 18 or more
• above-knee amputee, wearing a definitive ischial containment socket
• stump longer than 16cm
• wearing a liner, whatever the suspension system
• able to walk (d4600, d4601, d4602, d4608 accordinf to IFC)
• unilaterla or bilateral amputee
• able to done the socket standing
• whatever the etiology

Exclusion Criteria:

• protected person
• pregnant woman or nursing mother
• subject having comorbidities heavily impacting feeling or socket donning
• allergic to silicon
• suffering from big volume variations in a same day
• infecté stump (may lead to lymphatic problems)