When it is the injection needed
If rest, medications, and physical therapy do not relieve your pain, an injection of a local anesthetic and a cortisone preparation may be helpful.
What it is
Cortisone is a very effective anti-inflammatory medicine.
How is it injected
The physician carefully inserts a needle into the joint space in the shoulder and injects the cortisone solution. The solution goes into the joint space to reduce pain and inflammation in the joint.
Source from AAOS, Viewmedica, WebMD