Facet Joints of the Spine Anatomy Keith Bridwell, MD Orthopaedic Surgeon Washington University School of Medicine St. Louis, MO, USA

A joint is where two or more bones are joined. Joints allow motion (articulation). The joints in the spine are commonly called Facet Joints. Other names for these joints are Zygapophyseal or Apophyseal Joints. Each vertebra has two sets of facet joints. One pair faces upward (superior articular facet) and one downward (inferior articular facet). There is one joint on each side (right and left). Facet joints are hinge–like and link vertebrae together. They are located at the back of the spine (posterior). Facet joints are synovial joints. This means each joint is surrounded by a capsule of connective tissue and produces a fluid to nourish and lubricate the joint. The joint surfaces are coated with cartilage allowing joints to move or glide smoothly (articulate) against each other. These joints allow flexion (bend forward), extension (bend backward), and twisting motion. Certain types of movement are restricted. The spine is made more stable due to the interlocking nature to adjacent vertebrae.
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The article Dr. Keith Bridwell provide us with some basic anatomy of the spine which is important when patients and physicians are dealing with problems of the spine. Understanding the anatomy and biomechanics of the spine help physicians in determining the likely source of a patient's spine complaint. By obtaining a detailed history from the patient a physician can determine the location and the likely cause of a patient's complaint and then formulate a treatment plan to treat that particular problem. There have been studies which have determined which structures of the spine are capable of producing pain. These include the muscles, ligaments, zygapophyseal (facet) joints, the outer portion of the disc, nerve root and the vertebral bodies. Biomechanical studies have been performed to demonstrate when these particular structures are compressed or stressed. Using this knowledge and combining it with a history and physical examination can guide clinicians in determining what is the cause a patient's spine complaints and ways that it can be treated. For example, the facet joint is loaded or compressed on extension and unloaded and stretched on flexion. They have been found to be a source of pain in patients presenting with low back pain and can refer pain into the lower extremity but generally not below the knee. Many patients will complain of pain in their back on standing and walking that improves with bending forward and these patients tend to have increased pain when placed into extension on physical examination. The exam findings coupled with an explanation of the anatomy and basic biomechanics, can be reviewed with patient so that can fully understand and participate in their treatment. The treatment will be directed at minimizing stress to the painful area while improving the biomechanics by stretching structures that have become tight and strengthening the muscles that support and unload these painful areas. Occasionally, injections can be used to confirm the source of pain (by using an anesthetic) and controlling the symptoms to facilitate an active therapy program. It is clear that an understanding of anatomy and biomechanics can be very helpful to both patients and physicians in successfully treating spinal conditions. Gerard Malanga, MD

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