A cortisone shot delivers targeted treatment for pain and inflammation. It is usually injected into a joint, but other sites include tendons and the bursa surrounding the joint. Cortisone shots usually treat various types of arthritis, tendonitis, and bursitis, but they can be effective against other conditions, too.
Cortisone is a corticosteroid — synthetic drugs that resemble cortisol, a natural hormone produced by the adrenal glands. Cortisol affects many processes in the body, including blood sugar levels, metabolism, memory formation, and inflammation. Because cortisone is a synthetic version of cortisol, it has similar effects.
Inflammation is the process of white blood cells and other chemicals protecting the body from infection. In some diseases, the body mistakes healthy cells as foreign, which causes inflammation in otherwise healthy tissue and often leads to pain, redness, and warmth. A cortisone shot works by reducing the immune response, which decreases inflammation.
Doctors often refer to cortisone and other corticosteroids as "steroids," but they work much differently than hormone-related anabolic steroids that some people use as performance enhancers. The corticosteroids in a cortisone shot work by affecting the immune system, while anabolic steroids are synthetic substances that mimic testosterone. Anabolic steroids promote muscle growth and the development of male sexual characteristics.
Cortisone shots treat pain and inflammation associated with a variety of conditions. They are widely used for psoriatic, rheumatoid, reactive, and osteoarthritis. Physicians also use cortisone injections to treat other conditions affecting the joints, like bursitis, gout, tendonitis, and certain autoimmune disorders.
Risks of cortisone shot injections increase with long-term use and large doses. They include nearby bone death, cartilage damage, nerve damage, joint infections, ruptured tendons, lightening of the skin around the injection site, and thinning of the surrounding bone, skin, and soft tissue. Temporary side effects are facial flushing, increased blood sugar, and a brief flare of inflammation and pain immediately after the injection.
A cortisone injection is usually done in the doctor's office, but additional equipment, like an x-ray or ultrasound, is sometimes needed to guide the needle into place. The patient lies on an exam table, and the doctor cleans the injection site. Most of the time, a numbing agent is used to reduce injection pain. Some physicians also offer medication to help the patient relax, if necessary.
The cortisone is injected via a small needle. Depending on the condition, the shot goes into the bursa, joint, or next to a tendon. The bursa is a fluid-filled sac that cushions the area between the bones, tendons, and joints. For tendonitis, the injection goes into the tissue adjacent to the tendon. Imaging guidance is common for injections into joints. In some cases, the doctor removes excess fluid from the joint before injecting the cortisone.
After a cortisone shot, the pain decreases, but this initial effect is because of the numbing medication and wears off in the first few hours. The pain typically returns for a few days — it takes the cortisone injection between five and seven days to begin working. Once the effects kick in, some people experience a significant reduction in pain, while others find the symptom completely resolves. The pain may or may not return to baseline as the effects of the injection wear off.
While a cortisone shot is effective at reducing pain, there are some long-term effects to consider. Research shows that ongoing cortisone injections decrease cartilage volume in the knees and increase post-surgical infection risk significantly. Because cortisone weakens the immune system, many physicians limit injections to every three months for a single joint or a total of six injections per year.
The long term risks of cortisone shots should be weighed against short term benefits, though this greatly depends on what the injection is treating. For example, studies show that steroid injections are more effective at treating tendonitis than some other treatments, though there are no long-term benefits. Studies have also shown that overuse of cortisone injections for the treatment of arthritis in the knee may contribute to worsening outcomes, particularly since most patients live for decades following the onset of the condition.
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