The facet joints, as true synovial joints, were first postulated as an etiology of low back pain and sciatica more than 90 yr ago (1–3). It was not until 1933, however, that the facet joints themselves were reported to be the source of the back pain, at which time the term “facet syndrome” was coined by Ghormley (4). More recent studies have provided physiologic evidence that the facet joints do indeed cause back pain as well as referred pain to the buttocks and lower extremity in the lumbar region and the head and shoulder girdle in the cervical region (5–7). Back pain presumed caused by facet syndrome has been attributed to distension and inflammation of the synovial capsule, resulting in stimulation of nociceptive nerve fibers (6). Nerve root compression in the neural foramen or in the spinal canal may be caused by expansion of the synovial recesses (6, 8). Many studies have now described the successful relief of back pain after facet joint blocks (9–12).