Medial Branch Blocks are used as a diagnostic tool and usually give temporary relief of pain symptoms. Medial branch nerves are small nerves that feed out from the facet joints in the spine and carry pain signals from those joints. Facet joint injections are often used to identify a pain source; however, these injections do not always provide lasting pain relief. In such cases, it is beneficial to confirm that the facet joint is the source of a patient's pain. A medial branch nerve block temporarily interrupts the pain signal being carried by the medial branch nerves that supply a specific facet joint. If the patient has the appropriate duration of pain relief after the medial branch nerve block, that individual may be a candidate for radiofrequency neurolysis.