The Uncovertebral Joints are potential pain generators.

Uncovertebral joints (Luschka’s joints) are found from the 2nd cervical to the 1st or 2nd thoracic vertebra.

They appear between the uncinate processes and round edges of the vertebral body above.

There is some controversy whether they must be classified as true synovial joints. Some authors don’t see them as real joints but as a degeneration process within the intervertebral discs.

Most authors however see them as small synovial articulations. They are not seen at the age of 6 to 9 and they become fully developed before the age of 18.

The joints are located anteromedial to the mixed nerve root and posteromedial to the vertebral vessels and sympathetic nerve fibers.

They are the largest in the region C3-7 and smaller in the above and below regions.

Most joints begin to develop during the 6th week of fetal life and by the end of the 8th week they resemble adult joints. This is not seen in the uncovertebral joints.

Uncovertebral joints in the mid to lower cervical region extended further ventrally compared to the most cranial and caudal levels.

The uncovertebral joints limit posterior translation of the vertebra as well as lateral flexion.

They guide flexion and extension.

The major biomechanical function of uncovertebral joints includes the regulation of extension and lateral bending motion, followed by torsion, which is mainly provided by the posterior uncovertebral joints.

The uncovertebral joints are only found in bipedal animals and therefore primitive synovial joints that have formed as a result of our bipedalism.

The uncovertebral joints are potential generators of pain.

They are innervated by as well somatic as autonomic nerves. A loss of 50%-disc space in enough to damage the uncovertebral joints.

Their degeneration follows the degeneration of the discs because when the disc height diminishes, there is impaction of the uncinate process into the opposite fossa.

The joints then carry the weight of the head.

In degeneration of the joints, there is first a sharpening of the uncinate process and a rounding of its tip into a bulbous form (osteophytic nodule).

This osteophyte then impinges into the adjacent foramen.

These osteophytes only impinge on the nerve root after they have traversed at least 50% of the foraminal volume.

This happens mostly at the levels C4-6.

The uncovertebral joints may also be hypertrophic and cause inflammation of the perineurium and of the epidural adhesions. The combination of nerve root compression and inflammation may cause pain in a radicular distribution or radiculopathy.

The hypertrophy can also limit the flow of the vertebral artery.

Bibliography

Brismée JM, Sizer PS Jr, Dedrick GS, Sawyer BG, Smith MP.(2009) Immunohistochemical and histological study of human uncovertebral joints: a preliminary investigation. May 20;34(12):1257-63. doi: 10.1097/BRS.0b013e31819b2b5d.

Ying Yin, Xiaoxia Qin, Rongzhong Huang, Jing Xu, Yamei Li, Lehua Yu (2016)

Musculoskeletal Ultrasound: A Novel Approach for Luschka’s Joint and Vertebral Artery. Med Sci Monit; 22: 99–106. Published online Jan 10. doi: 10.12659/MSM.896242

Narayan Yoganandan, Sagar Umale, Brain Stemper, Bryan Snyder. (2017) Fatigue responses of the human cervical spine intervertebral discs. Journal of the Mechanical Behavior of Biomedical Materials 69, 30-38.

Zhong Wang, Hui Zhao, Ji-ming Liu, Li-wen Tan, Peng Liu, Jian-hua Zhao. (2016) Resection or degeneration of uncovertebral joints altered the segmental kinematics and load-sharing pattern of subaxial cervical spine: A biomechanical investigation using a C2–T1 finite element model. Journal of Biomechanics 49:13, 2854-2862.