Facet joint pain is pain experienced in the facet joints, which are the paired joints that help hold together and limit movement between adjacent vertebrae in the spinal column. These articulations are found between the paired spinous processes projecting downward and backward from the body of each vertebra like large prongs, with the joint occurring between the superior articular process on one vertebra and the corresponding inferior articular process of the vertebra above it. Pain at this joint, most common in the low back, is typically a symptom of facet joint syndrome, a condition in which the joint has degenerated, often as a consequence of osteoarthritis.
Also known as zygapophyseal or Z-joints, facet joints are a type of synovial or movable joint called an arthrodial or gliding joint. In a gliding joint, the articulating surfaces are normally flat, which allows them to slide slightly past one another. Facet joint pain is felt between these adjacent bony surfaces — specifically the vertical articulation between the posterior or rear surface of the superior articular process of the lower vertebra and the anterior or front surface of the inferior articular process of the vertebra above it.
At each spinal motion segment, which is formed by a pair of adjacent vertebrae and the joints between them, including both the facet joints and the intervertebral joints between the bodies of the vertebrae, is a pair of Z-joints. These joints are responsible for controlling and limiting excessive movement at their motion segment, particularly excessive rotation, or twisting from side to side, forward-bending, and anterior translation, or the sliding forward of one vertebra relative to the vertebra below it. When facet joint pain is experienced, it is often while the joint is pushed to its limit.
Facet joint pain, as a consequence of facet syndrome, is experienced when the joint structures degenerate and place pressure on the nerves there, either by the wearing of the disk between the bones of the joint or by other damage to the joint capsule, which contains the synovial fluid that lubricates and nourishes the joint. This condition is said to be secondary to another condition, that of degeneration of the intervertebral disks. When the disks between the stacked bodies of the vertebrae wear down, a result of age, obesity, injury, or disease, this is known as degenerative joint disease or osteoarthritis. This condition can cause damage to the nearby facet joint as the two bones become compressed and can place stress on the many nerves running between the two joints, resulting in the symptom of facet joint pain.