The Anatomy of the Spine: The Vertebral Joints
The joints of the vertebral column include the joints between the bodies of adjacent vertebrae and joints between the adjacent vertebral arches. Two types of joints in the neck are given special attention because they’re different from other joints: the atlanto-occipital joints and the atlanto-axial joints in the upper cervical region. These joints between the first two cervical vertebrae and the cranium permit a greater degree of movement than the rest of the vertebral column. The vertebrae also articulate with the ribs and the hip bones.
Atlanto-occipital joints: Joining the head and the atlas
Atlanto-occipital joints are synovial joints located between the occipital condyles and the superior articular surfaces of the lateral masses of the atlas. You have two atlanto-occipital joints, which allow you to nod your head. They’re held in place by the anterior and posterior atlanto-occipital membranes, which help prevent excessive movement of the joints.
Atlanto-axial joints: Joining the atlas and axis
The three atlanto-axial joints are also synovial joints. One is found between the dens (odontoid process) of the axis (2nd cervical vertebra) and the anterior arch of the atlas (1st cervical vertebra), and two are located between the lateral masses of the 1st cervical vertebra and the superior articular facets of the 2nd cervical vertebra.
The following four ligaments stabilize these joints:
Apical ligament: Connects the dens (odontoid process) to the foramen magnum of the occipital bone
Alar ligaments: Connect the dens (odontoid process) to the lateral margins of the foramen magnum
Cruciate ligament: Attaches the dens (odontoid process) to the anterior arch of the atlas and the body of the axis to the foramen magnum of the occipital bone
Tectorial membrane: Starts at the skull and becomes the posterior longitudinal ligament
Intervertebral joints: Joining other vertebrae to each other
Intervertebral joints, which connect adjacent vertebrae, include both synovial and cartilaginous joints.
Intervertebral synovial joints: These joints are found between the superior and inferior facets of adjoining vertebral arches. They are supported by the following ligaments:
The interspinous ligament runs between the spinous processes.
The supraspinous ligament connects the tips of the spinous processes and forms the strong nuchal ligament that runs posterior to the cervical spine.
Intertransverse ligaments connect the adjacent transverse processes, and the ligamentum flavum connects the laminae of adjoining vertebrae.
Intervertebral cartilaginous joints: A fibrocartilaginous joint is formed between the adjacent vertebral bodies with fibrocartilaginous intervertebral discs located between the bodies. Each disc is made up of a gelatinous mass, the nucleus pulposus, which is surrounded by the annulus fibrosus (which is made up of tough fibrous layers).
Anterior and posterior longitudinal ligaments run in bands down the anterior and posterior surfaces of the vertebral bodies from the skull to the sacrum. They help to stabilize the vertebral column.
The sacrum articulates with the hip bones to form the sacroilliac joints. The superior surface of the sacrum has two superior facets that articulate with the inferior articular processes of the 5th lumbar vertebra.
The sacrococcygeal joint is formed between the coccyx and the sacrum. It has an intervertebral disc and is stabilized by sacrococcygeal ligaments.