The sarcopenia diagnosis is based on the muscle mass and on impaired physical performance. The emerging field of ultrasound assessment of muscle mass in older patients is based on 2d parameters with prediction equations for muscle mass. For the moment, validation of prediction equations in older adults with varying function and health is lacking. The study aims to evaluate correlation of muscle mass between 3D muscle mass measurement and DXA, in order to dispense with the prediction equation.

Older patients who agree to participate to the study will undergo 3D ultrasound muscle mass measurement, 2D panoramic mode muscle mass measurement and biphotonic X-ray absorptiometry assessment. Correlation analysis will be done with the different measurement.

Inclusion Criteria:

• Patients over 75 years old
• Osteoporosis diagnosis confirmed by Dual-energy X-ray Absorptiometry

Exclusion Criteria:

• Neurocognitive disorders preventing the expression of informed consent
• Patients who cannot undergo an examination in a static position
• Lack of a measurement site (muscle resection or amputation)
• Any state of dehydration or water inflation
• Patient with legal protection measure

Older patients who agrees to participate to the study will undergo 3D ultrasound muscle mass measurement, 2D panoramic mode muscle mass measurement and biphotonic X-ray absorptiometry assessment, the same day. Correlation analysis will be done with the different measurement.