A medial branch block is primarily a diagnostic procedure where a physician injects a local anesthetic onto the medial branch nerves that supply the facet joints. Facet joints are part of the framework of the spine that allow you to twist from side-to-side. Occasionally, the facet joints can become irritated or inflamed.
If you notice a decrease in pain after the injection, the specialist can now deduce that your facet joint is likely the source of your pain. However, the local anesthetic normally only lasts a few hours to a few days. For longer-term relief, the specialist may choose to implement another procedure called a radiofrequency ablation.