Your shoulder joint is composed of three bones: the clavicle (collarbone), the scapula (shoulder blade), and the humerus (upper arm bone). Your shoulders are the most movable joints in your body. They can also be unstable because the ball of the upper arm is larger than the shoulder socket that holds it. To remain in a stable or normal position, the shoulder must be anchored by muscles, tendons and ligaments. Because the shoulder can be unstable, it is the site of many common problems. They include sprains, strains, dislocations, separations, tendinitis, bursitis, torn rotator cuffs, frozen shoulder, fractures and arthritis.

Usually shoulder problems are treated with RICE. This stands for Rest, Ice, Compression and Elevation. Other treatments include exercise, medicines to reduce pain and swelling, and surgery if other treatments don’t work.

Source
NIH: National Institute of Arthritis and Musculoskeletal and Skin Diseases

Shoulder Injections for Pain Relief

This outpatient injection procedure relieves pain in the shoulder and arm caused by arthritis or other damage to the shoulder joint.

Preparation

The patient lies down, and the shoulder is cleaned and sterilized. Local anesthesia is administered to numb the tissue at the injection site.

Needle Insertion

The physician may use an x-ray device called a fluoroscope to guide a needle to the shoulder joint. Contrast dye is injected to confirm the needle’s position.

Pain Relief Injection

A mixture of anesthetic and steroid medication is injected into the joint to reduce inflammation and relieve pain.

End of Procedure

The needle is slowly withdrawn, and the injection site may be covered with a small bandage. Extended pain relief usually begins within two to three days of the injection. In some cases it may be necessary to repeat the procedure up to three times to recieve the full benefits of the treatment.