Shoulder pain is a common reason for medical consultation affecting 6.7 % of the adults from 50 to 70 years old and until 21 % of the adults over 70. Among these painful shoulders, rotator cuff tendinopathy represents 44 to 65% of these consultations. To treat this condition, patients usually receive analgesics and physical therapy. When these treatments are not effective, a corticosteroid sub-acromial injection is proposed. However, according to the literature, there is only about 50% of good response to this subacromial injection in rotator cuff tendinopathy. It has been suggested that the injection could be more effective in the presence of an inflammation over the tendons called bursitis. However, no studies have clearly established this. The objective of the study is to determine if the presence of a bursitis could be a factor of good response to corticosteroid injection. The results could allow us to determine which patients have the best profile to respond to subacromial injection. The investigators hope that these data would improve the treatment of this frequent disease.

Patients referred to receive a subacromial ultrasound-guided injection for shoulder pain related to a rotator cuff tendinopathy will be enrolled in the study. After validation of the inclusion criteria, the participants will receive oral information about the protocol. Then, they will be examined and will undergo X-rays and an ultrasound of their shoulder. Pain shoulder and shoulder disability will be assessed before the injection with a visual analogic pain scale and the Oxford Shoulder Score questionnaire, respectively.

The subacromial injection will be performed under ultrasound guidance to accurately inject the subacromial bursae. After skin disinfection with povidone, the injection will be performed with a 21G needle. The bursae will be injected with 2 ml of lidocaine 2% and 1 ml of betamethasone.

After the procedure, the participants will all receive a standardized physiotherapy.

For primary outcome, the therapeutic response will be assessed 3 months after the procedure. Patients will be considered as having a good response if their level of pain decreases by over 30%.

The number of participants having a good clinical response will be compared between the patients presenting a bursitis and those without bursitis. The comparison will be made using a Chi-2 test.

Others parameters will be studied: reduction in pain 6 weeks after the injection, reduction in shoulder disability 6 weeks and 3 months after the injection. Other ultrasound lesions will be collected so as X-ray features to search other factors associated with the presence or absence of a good therapeutic response (details in secondary outcomes).

Inclusion Criteria:

• Major patients with manifestations of rotator cuff tendinopathy referred to our rheumatology department to receive an ultrasound-guided subacromial injection.

Exclusion Criteria:

• Patients refusing to participate
• Allergic to local anesthetics
• Shoulder involvement of an inflammatory rheumatic disease
• History of shoulder surgery
• Shoulder instability
• Glenohumeral osteoarthritis
• Frozen shoulder
• Extended rotator cuff tear
• Tendinous calcification > 0.5 cm
• Pregnant women
• Minors
• Majors under guardianship
• Patient inappropriate for entry into this study according to the judgment of the investigator

Patients who will receive a subacromial ultrasound-guided injection for shoulder pain related to a rotator cuff tendinopathy