[Imaging in chronic low back pain: which one and when?].

Non-specific low-back pain (LBP) should de differentiated from symptomatic LBP, attributed to recognisable, known specific pathology (e.g. tumour, infection, inflammatory disease...). The initial clinical history taking should aim at identifying "red flags", associated with a higher risk of serious disorders. Rapid MRI of the spine should be performed in order to make a specific diagnosis. In chronic LBP, X-rays of the spine are always performed, first to rule out underlying specific diagnosis, then to describe degenerative spine changes. At MRI and X-rays, most of degenerative disc abnormalities are non-specific, frequently found in the asymptomatic subjects. On fat-suppressed T2WI, edema of endplates in degenerative disc disease and of posterior arches in facet arthropathy and spondylolysis is well-correlated to LBP. Such edema may be useful to guide the treatment.