The facet joint of the spine is a moveable connection that connects one vertebral body to another. This injection includes both a long-lasting steroid and an anesthetic such as lidocaine or bupivacaine. The steroid reduces the inflammation and irritation and the anesthetic works to numb the pain. The first time the injection is done, it is done for both diagnostic and therapeutic purposes.
If your pain disappears with the injection then it is clear that the pain is originating from the joint, and it has been shown that therapeutic lumbar facet joint nerve blocks with local anesthetic, with or without steroids, may be effective in the treatment of chronic low back pain of facet joint origin. Though, even if your pain does not get better, this is also useful information as the face joint can be ruled out as a pain generator.
The most important and greatest success achieved with the use of facet injections is the rapid relief of symptoms that allows patients to experience enough relief to become active again. With this they regain the ability to resume their normal daily activities that was not achieved with oral medications and physical therapy.