A facet joint block, and/or medial branch block, is an injection into the joint in the back called the facet joint. The facet joints are paired structures on either side of the spine at a particular spinal level. The facet block is frequently done at more than one adjacent joint in the spine at the same time. This may eliminate the patient's spine pain and therefore demonstrate that the pain is coming from the specific facet joint area. This test is performed on selected facet joints in an anatomic region of the spine (cervical, thoracic, lumbar).