Syndromes, Injuries and Diseases   Lumbar and Cervical Facet Syndrome Bones of the spine articulate anteriorly by intervertebral disks and posteriorly by paired joints. These posterior paired joints are commonly termed facet joints, more formally termed zygapophyseal joints. Facet joints are true synovial joints, with a joint space, hyaline cartilage surfaces, a synovial membrane, and a fibrous capsule. Two medial branches of the dorsal rami innervate the facet joints. Medial branches of the lumbar dorsal rami issue from their respective intervertebral foramina, cross the superior border of the transverse process, and then run medially around the base of the facet joint before innervating the joints. In recent studies, nociceptive substance P immunoreactive nerve fibers and autonomic nerves have been identified in the lumbar facet joint capsule and synovial folds. Douglas et al identified substance P immunoreactive nerve fibers in erosion channels extending through the subchondral bone and calcified cartilage into the articular cartilage. Giles and Harvey identified them in the inferior recess capsule and synovial folds, whereas Ashton et al identified them running freely in the facet capsule stroma. Gröblad et al demonstrated sparsely distributed substance P immunoreactive nerve fibers in facet joint plical tissue. The presence of nociceptive nerve fibers in the various tissue structures of facet joints and the presence of autonomic nerves suggest that these structures may cause pain under increased or abnormal loads. Substance P is a well-known inflammatory mediator that may sensitize nociceptors to them and other mediators, resulting in chronic pain. Like other joints, the facet joints consist of bone, cartilage, synovial tissue, and menisci that are rudimentary invaginations of the joint capsule. In the synovial fluid of patients with rheumatoid arthritis, osteoarthritis, or traumatic joint disease, increased levels of prostaglandins have been measured and implicated as an important cause of pain. Prostaglandin, a known inflammatory mediator, is also released from facet joints. Biomechanically, facet joints assume a prominent role in resisting stress, and their importance is well established. A cadaveric study by Adams and Hutton demonstrated that the facet joints resist most of the intervertebral shear force and share in resisting the intervertebral compressive force, albeit only in lordotic postures. In rotation of the spine, the facet capsular ligaments are by far the most strained among the various spinal ligaments. They protect the intervertebral disks by preventing excessive movement. Frequency: In the US: The prevalence of facet joint pain in the general population or in those with acute back pain has not been investigated. The reported rate of facet joint pain for patients with chronic LBP ranges from 4-75%. The reported prevalence seems to be a function of the size of the sample studied and the conviction of the authors. Three studies report the prevalence of lumbar facet joint pain among chronic LBP patients based on 100% relief of pain using less than 2 mL of intra-articular diagnostic injection. In 1988, Jackson et al reported 7.7% of 454 patients with chronic LBP had 100% relief with diagnostic injection. In 1991, Carette et al reported that 11 (5.8%) of 190 patients experienced complete relief of symptoms with a single lidocaine injection. In 1994, Schwarzer et al reported that 7 (4%) of 176 patients reported 100% relief. This latter study was more stringent than the former in that Schwarzer et al performed a second confirmatory block with bupivacaine, documenting longer relief of pain commensurate with the longer half-life of the local anesthetic. When less stringent criteria are used, higher prevalences are reported. In 1988, Moran et al reported relief in 9 (16.7%) of 45 patients using 1.5 mL of bupivacaine. Pain provocation followed by pain relief with local anesthetic was used as the diagnostic criterion. In 1992, Schwarzer et al reported relief in 9 (9.7%) of 92 patients using 50% reduction of pain and double-block screening with lidocaine and confirmatory bupivacaine block. In a separate investigation, they reported a prevalence of 26 (15%) of 176 patients using the same diagnostic criteria. In yet another study, Schwarzer et al reported 23 (40.3%) of 57 patients obtained 50% or more pain relief with bupivacaine but no relief with saline control injection. A 2004 study by Manchikanti et al reported a lumbar facet prevalence rate of 27% using controlled comparative local anesthetic blocks of the dorsal median nerves. Higher prevalence rates are reported when control blocks are not used. In 1984, Raymond and Dumas reported a 16% prevalence rate using a strict intracapsular technique but no control block. In 1992, Revel et al reported 22 (55%) of 40 subjects had 75% or more relief of pain and 17 (42.5%) of 40 patients had greater than 90% relief of their pain with a single intra-articular lidocaine injection. As seen from these data, reports of prevalence are a function of the investigators' choice of selection criteria. Studies requiring the most stringent 100% relief of symptoms after a diagnostic block report a 4-7.7% prevalence rate of facet joint pain among chronic LBP patients. Studies using double blocks requiring 50% relief report prevalence rates of 9-15%. Numerous other studies using a single diagnostic block report prevalence rates from 16-75%. Cervical facet pain is often related to whiplash type of injuries in the cervical spine and is more often a post-traumatic finding than in the lumbar spine.