What are corticosteroids?
Corticosteroids are a class of medications related to cortisone, which is a naturally occurring hormone produced by your adrenal glands.  After injection, cortisone works to reduce inflammation (heat, redness, swelling, and pain).

How are the injections given?
An ultrasound machine is used to identify the joint.  The skin is then sterilized with an alcohol-based solution, and local anesthetic is used to numb the skin.  A needle is then directed into the joint under direct visualization using the ultrasound machine.  The advantage of ultrasound is the precise placement of the medications.  A study published in the Journal of Rheumatology in 2004 showed that ultrasound guidance improved outcomes in patients with painful shoulders.1

Does the injection hurt?
The injections are relatively comfortable and as pain free as a simple blood test or injection into the muscle in the arm.

What should I feel after an injection?
When the local anesthetic wears off, it is common to feel a mild increase in discomfort in the joint that resolves within 24 hours.  You may treat this discomfort by applying an ice pack and by using medications such as acetaminophen or ibuprofen.

How long does it take for the injection to work?
Most injections typically take 48-72 hours to take full effect, but the local anesthetic given with the cortisone will give some improvement immediately.

How often may I have repeat injections?
There is some controversy that too many injections may weaken tendons, ligaments, and accelerate the loss of cartilage.  However, other studies have found that injections can slow joint damage and help preserve the joint.  A reasonable approach is to limit the frequency of injections to 3-4 for a single joint per year.

What are the possible side effects of an injection?
Most joint injections result in no side effects.  Side effects that rarely occur include injury to the joint or tendon, thinning of the skin, loss of skin color, calcification around the joint, and joint infection.  The joint pain occasionally flares up briefly after an injection.  Systemic effects may occur due to absorption of the corticosteroids from the joint, the most common being elevated blood sugar in a diabetic patient.

1 Naredo E. A randomized comparative study of the short-term response to blind injection vs. sonographic guided injection of local corticosteroids in patients with painful shoulder. Journal of Rheumatology. 2004;31:308 14.