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John Gibbons is a registered Osteopath, Lecturer and Author and is discussing the anatomy of the facet joints.

Facet joints are also known as zygapophyseal, apophyseal or Zjoints. There are approximately over 100 facet joints within the vertebral column and they form as a set of synovial joints that are located between the articular processes of two adjacent vertebra. The facet joint is truly unique and a crucial anatomical area of the spine that allows articulation between each vertebra as well as assisting to transfer the load that the column experiences each and every day of our busy lives.

The facet joint is a diarthrodial (synovial) joint which has opposing articular cartilage and is surrounded by a ligamentous capsule that protects and encases the joint space. The facet joints in a nutshell allow the vertebral column to move in all planes of motion. However, depending on their location, the facet joints will also restrict motion because of their orientation and as such act as a type of active ligament. For example, within the lumbar spine we can perform flexion and extension with relative ease without too much restriction because the facet joint will open and close to allow these movements.

However, because the lumbar facet is more vertically orientated within the lumbar spine, rotation is limited because of this design. Roughly speaking there are approximately only 12 degrees of segmental rotation permitted within the lumbar spine, however, the cervical spine has substantially more rotation in comparative terms, simply because of the way the facet joints are orientated.

The facet joint is formed by two adjacent vertebral with the superior facet of the vertebra above articulating with the inferior facet of the vertebra below. Within the cervical spine the facet joints are more orientated within a horizontal plane, hence the reason for increased rotation. As they travel down to the lower thoracic and lumbar spine the facet joints gradually become more vertically orientated, hence rotation in the lumbar spine is limited.

This change of facet orientation that restricts the motion in certain planes is simply to protect the intervertebral discs and spinal cord from undue and excessive motion. If it wasn’t for the unique alignment of the facet joint the vertebral column would wear down rather quickly, leading to a condition known as spondylosis (osteoarthritis of the spine).

It is important for the reader that they understand the orientation of each level of the vertebral column (as shown in the table below), especially when it comes to applying manual therapy techniques. For example, it is more common to use a rotation type of thrust to the cervical spine to cavitate the joint space. However, in the lumbar spine we might apply a side bending type of thrust because of the limited rotation due to the facet orientation, and if we decided to apply more of a rotatory thrust then the facet joints might become impacted and potentially cause more pain to the patient. Furthermore, a cavitation would now not be possible because you are forcibly closing the joint rather than physically trying to open the joint, which typically causes the cavitation noise.

Cervical facet joints

All movements are possible within the cervical region: flexion, extension, rotation and lateral flexion. This is because the facet joints are orientated around 45 degrees to the frontal plane. The superior articulating surface will face posterior, superior and medially and the inferior articulating facet will face anterior, inferior and laterally.

Thoracic facet joints

The thoracic spine has less range of motion in all planes, especially flexion and extension as compared to the cervical spine. This is partly due to the associated rib cage and the fact that the facet joints between adjacent thoracic vertebrae are angled at 60° to the transverse plane, with the superior facets facing posterior, superior and laterally and the inferior facets facing anteriorly, inferiorly, and medially.

Lumbar facet joints

The facet joints in the lumbar region lie 90 degrees in the sagittal plane, the superior articular facets face medially, and the inferior articular facets face laterally. However, there is a slight change or the orientation at the lumbosacral (LS) junction, as this modification keeps the vertebral column from sliding anteriorly in relation to the sacral vertebra (S1) that is located directly below.