The facet joints are the moveable joints of the spine that connect one vertebra to another vertebra. Without the facet joints, you would not have flexibility in the spine, and you could only move in very straight and stiff motions.
The facet joints can get inflamed due to injury or arthritis, which can cause pain and stiffness. When the facet joints are affected it typically causes pain not only at the site of the facet joint, but the pain may also radiate to the head, shoulders, buttocks and legs. To relieve this pain, a doctor may administer a facet joint block.
During a facet joint block, a local anesthetic and a steroid are injected into a facet joint. This procedure is both a type of treatment and a test, called a "therapeutic trial". This means that while the doctor is seeking to relieve the symptoms, he or she is also making sure that the area being treated is the source of the pain. If the pain goes away, the doctor can assume that the facet joint is the source of the problem.