An injection of a small amount of cortisone and an anesthetic into the bony spinal canal to reduce the inflammation of the nerves in the spine and ease the discomfort of lower back pain. Although cortisone is a strong anti-inflammatory medication, the procedure is not always successful, and that is especially true for people with long-standing back pain. Epidural steroid injections tend to be given, often in a timed series, if more conservative measures are not effective in relieving back pain. The injections are sometimes given to try to avoid back surgery.