steroidal injections

My uncle who has problems in the lumbar part of the back is taking steroid injections. What are these injections used for exactly? He has already had 2, and needs one more! I would like to know how they work!!! Can anybody explain to me!!!!??? Thanx

Lumbar steroid injections are used to treat nerve inflammation which causes back pain, and even neck, shoulder, arm, or leg pain. An epidural steroid injection is an injection of steroidal medication to the epidural space (it is a space that surrounds the membrane that covers the spine) to reduce the swelling of the nerve roots and in that way bring relief for several weeks or months but it can not provide permanent pain relief. It is just a cover up until the cause of the pain is removed.