Osteoarthritis is a degenerative disease of hyaline cartilage not associated with an infection or an inflammatory process that affects millions of people. The first symptoms usually appear from 40-50 years and at this point, conventional radiological tests provide diagnostic elements relatively late, poorly correlated with pain relief and providing no functional information. In this context, there is a real need for imaging techniques for early detection of osteoarthritic changes in a still reversible stage for faster support and MRI appears to be the tool of choice.

Conventional proton MRI sequences already allow improved detection possibilities compared to conventional radiology and CT arthrography supplanted. They nevertheless remain insufficient to identify incipient lesions or paradoxically to the point of too advanced lesions. Due to recent technological advances, exploration MRI other nuclei such as sodium is now possible. Quantitation of sodium in the cartilage by sodium MRI allow quantifying proteoglycan loss and ultimately a gradation osteoarthritic reached.

This project's main objective is to quantify the biochemical changes (sodium content) occurring at different stages of osteoarthritis defined by clinical algofunctional scores (Lequesne) and conventional radiographic scores (Kellgren and Lawrence).

Inclusion Criteria:

• Patient with osteoarthritis

Exclusion Criteria:

• patient with contraindication for MRI