Since biological disease-modifying anti-rheumatic drugs (bDMARDs) are available in rheumatoid arthritis (RA) strategy an emerging question is the definition of remission in RA. Today some criteria were already proposed and the last one was proposed in 2011.

All these criteria integrated only clinical criteria without imaging assessment. In this context, ultrasound joint is daily performed without definition of remission. A discrepancy exists between clinical remission and persistence of active disease with ultrasound joint presence of a Doppler effect indicating inflammation and the risk of progression of joint damage. A definition of remission in RA could include erosions regression in subchondral bone (at best measured by high resolution peripheral quantitative computed tomography (HR-pQCT)).

The main hypothesis is that the reduction of erosion size assessed by HR-pQCT will be observed only in the absence of local inflammation measured by Doppler ultrasound in the erosion.

Tumor Necrosis Factor (TNF) blockers have strongly improved RA therapy outcome in terms of clinical improvement and structural damage (progression of radiographic lesions). Recent data showed that there could be joint bone rebuilt in case of inflammation suppression. HR-pQCT is a new technique emerging for bone erosions assessment in RA. Erosions size and volume could be reduced with anti-TNF, but with a large interindividual variability. There was no correlation between the activity of clinical or ultrasound synovium and evolution of erosion HR-pQCT.

Inclusion Criteria:

• Initial medical examination performed,
• RA diagnosis according to the criteria of the ACR / EULAR 2010
• Low or moderate disease activity with a DAS28 ≤ 4 since at least for 6 months
• Patients with bDMARDs (Remicade®, Enbrel®, Humira®, Cimzia®, Simponi®, Ro-Actemra®, ou Orencia®) since at least 6 months and no change planned by the investigator,
• Patient with at least one erosion on the head of the 2nd or 3rd metacarpal right or left,
• Stable corticosteroids dose since at least 3 months less than or equal to 10 mg of prednisone equivalent,
• Medical care and monitoring in the rheumatology department of the CHU of Saint-Etienne or the Edouard Herriot Hospital in Lyon,
• written consent of patient

Exclusion Criteria:

• Other diagnosis than RA,
• Intravenous or intra-articular injection at the 2nd or 3rd metacarpophalangeal left or right during the 3 months prior to inclusion,
• Surgery provided at the 2nd or 3rd metacarpophalangeal right or left within a year of inclusion,
• Concomitant treatment with zoledronic acid (Aclasta) or denosumab (Prolia®)
• Refusal of blood collection,
• Pregnancy or breastfeeding women,