A Medial Branch Block is a diagnostic procedure to help locate the source of pain. The procedure bathes the medial branch nerves, which attach to the spine’s facet joints, with numbing medicine. The medial branch nerves can cause pain when the facet joints of the spine are injured or diseased. The injection helps find the source of your pain and may relieve your pain for a brief time. If the injection area is the source of pain, there is immediate relief but soon wears off. If the block is successful, the doctor can then recommend a procedure for long-lasting relief.