The main objective of the study is to determine the Minimal Clinically Important Difference of the "Functional Reach Test" in the Elderly by a statistical method.

The first secondary objective of the study is to determine the Minimal Clinically Important Difference by the Anchor method based on a qualitative assessment by the patients of their own response. The second secondary objective is to determine the Minimal Clinically Important Difference by the Delphi method, based on the search for a consensus between physiotherapists specializing in geriatrics.

The French population is aging, and geriatric rehabilitation care must adapt to this growing population. The functional reach test is a common clinical test in geriatrics. It helps to determine the risk of falling. However, its metrological qualities are not all determined. The Minimal Clinically Important Difference (MCID) is in particular unknown for this test. The MCID of a test makes it possible to personalize in a way more in-depth evaluation of physiotherapy treatment. So it is necessary to characterize this essential metrological determinant of a common balance skills assessment tool.

Inclusion Criteria:

• People over 65 years old
• People in care with balance problems

Exclusion Criteria:

• People in an emergency situation
• People unable to give their consent (including people under guardianship)
• Patients already involved in another study.

The subjects recruited are patients aged over 65, having balance problems.