The uncovertebral joints, also known as the joints of Luschka or neurocentral joints, are the four pairs of synovial joints between the vertebrae C3-C7. They are found lateral and anterior to the intervertebral foramina, on each side of the relevant intervertebral discs.
The function of the uncovertebral joints is to follow the movements of the cervical spine, but as well to control these movements and stabilize the neck. The uncovertebral joints have a special place in the world of physiotherapy, as they often can undergo arthritic changes, which due to their location can affect the spinal nerves and alter the movements between the relevant vertebrae.
|Articular surfaces||Uncinate processes C3-C7 and inferior aspect of the respective vertebra above|
|Innervation||Spinal nerves C3-C7|
|Blood supply||Vertebral artery|
|Movements||Slight movements following that of the cervical spine|
This article will discuss the anatomy and function of the uncovertebral joints.
The uncovertebral joints are the small articulations between the lateral parts of the vertebral bodies C3-C7. The articular surfaces that comprise each joint are covered with articular cartilage and they are formed by:
- The uncinate (neurocentral) process of the vertebrae C4-C7;
- The lateral part of the inferior aspect of the vertebrae C3-C6.
Since the articular surfaces are present only on the C3-C7 vertebrae, there are four pairs of uncovertebral joints between them in total. The uncinate processes are the small triangular bony projections that arise from the lateral part of the superior margins of vertebrae C4-C7. Each uncinate process articulates with the corresponding surface of the vertebra above.
The corresponding articular surface of the vertebra above is beveled in shape so that it fits the shape of the uncinate process that it articulates with. The atlas (C1), axis (C2) and the vertebra C3 do not have an uncinate process, thus they do not feature the uncovertebral joints.
Each uncovertebral joint is enclosed by a fibrous capsule that is continuous medially with the corresponding intervertebral disc. In the inner surface of the fibrous capsule, a large number of synoviocytes are observed, confirming the fact that these joints are truly synovial.
The uncovertebral joints do not have ligaments intended specifically for their support, but are rather stabilized by the ligaments of the cervical spine, such as anterior and posterior longitudinal ligaments. The uncovertebral joints are respectively innervated by the cervical spinal nerve of their corresponding segment. Their blood supply comes from the vertebral artery.
The movements on the uncovertebral joints are minimal and they generally follow the movements of the cervical spine as a whole. During lateral flexion of the neck, the space between the articular surfaces of the contralateral uncovertebral joints widen. Conversely, the space of the ipsilateral uncovertebral joints shortens so that their articular surfaces physically come in contact with each other. Due to this, these joints stabilize the neck by physically limiting the lateral flexion of the cervical spine.
Moreover, the uncovertebral joints smoothen the flexion and extension of the neck by preventing the movement to fall out of the straight line while being carried.
Uncovertebral joint hypertrophy
The uncovertebral joints are almost always affected by hypertrophic arthritis after the age of 65. In most cases, the appearance of osteoarthritis doesn’t have any obvious cause. The earliest changes in osteoarthritis are the deformation of the articular cartilage, which becomes increasingly thinner over time due to decreased ability of chondrocytes to regenerate.
The subchondral bone becomes exposed and prone to chronic mechanical injuries, which usually results in the growth of osteophytes (bone spurs) at the margins of the joint. Given that the uncovertebral joints are found lateral and anterior to the intervertebral foramina, the osteophytes within them may impinge the cervical spinal nerves and the vertebral artery. In this case, surgical resection of the osteophytes successfully removes the compression.