A corticosteroid or steroid injection is used to reduce inflammation in muscles and joints. It is often used to treat conditions such as arthritis, tendinitis, bursitis, and more specific conditions such as de Quervain's tenosynovitis and carpal tunnel syndrome. It also may be used to treat allergies or asthma.
The procedure is done by injecting corticosteroid directly into the affected area. The area might be painful for up to 2 days after the injection, but most people have improvement after 2 days.