Bone fracture occurrence is associated with an increasing of morbidity and mortality. Some factors of fracture occurrence have been highlighted. For example, some diseases or therapy are known to increased risk of bone fracture only in some patients. Accordingly, it is important for clinicians to identify patients at risk for bone fracture. Right now, various tools are available for the clinicians:

• clinical exam,
• bone mineral density assessed by Dual Energy X-ray Absorptiometry (DEXA),
• an algorithm based on interrogation, clinical exam and bone mineral density. However, prediction of bone fracture risk needs to be improved since only 50% of bone fractures can be predicted. DEXA provides information for fracture risk estimation, but it is unable to distinguish cortical part to trabecular part. It also fails to quantify the microstructural properties that influence bone strength. Bone microarchitecture, including the cortical compartment can now be assessed in vivo by the HR-pQCT. This technique allows access to several parameters: on the one hand the volumetric bone mineral density for the whole area measured as well as cortical and trabecular regions, and on the other hand, the thickness and cortical porosity and the number of trabecular, their orientation and distribution.

Thus, the HR-pQCT allows realizing a virtual bone biopsy and provides information on cortical and trabecular bone microarchitecture. This is the only noninvasive way to assess cortical and trabecular bone microarchitecture.

Inclusion Criteria:

1. For patients:

   1.1.Women or Men taken in charge in Saint-Etienne' Hospital and one of the following pathologies: 1.1-a : Osteoporosis defined as: history of fracture by bone fragility documented 1.1-b : Bone Fragility: Patient with the indication of bone densitometry without a fracture history 1.1-c Articular inflammatory disease: Rheumatoid Arthritis, Spondyloarthritis 1.1-d Endocrine diseases : Primary Hyperparathyroidism, Constitutional Thinness, Anorexia nervosa 1.2. written consent

2. For controls:

2.1. Episode of acute back pain or radicular pain (lasting for less than a month) with taking corticosteroid less than 1 month 2.2. written consent

Exclusion Criteria:

drugs induced bone loss: 1.1.Anti-aromasine or GnRH agonist for at least 6 months, 1.2. Corticosteroid therapy 1.3. Antiepileptic carbamazepine, phenobarbital, phenytoin, primidone, valproic acid for at least 6 months) 2. fracture due to bone fragility 3. drug with bone effect (bisphosphonate, teriparatide, strontium ranelate)