Typically, doctors want to make sure that the facet joint is the cause of your pain before going in and burning the nerve supply to that facet joint with the radiofrequency ablation. The first injection is usually with a short-acting anesthetic, such as lidocaine, to determine if there is immediate relief of pain after the injection. If there is a positive response, then a second injection is administered at a later date using a different, more long-acting anesthetic, such as bupivacaine. This helps to rule out a false positive response to the initial injection. If there is a sufficient amount of relief with both injections, then it is more likely that the facet joint is the cause of the pain.