Intervertebral Joints

Intervertebral joints are the articulations between adjacent vertebrae in the vertebral column. These joints are essential for providing stability, shock absorption, and flexibility to the spine. Each intervertebral joint consists of two main components: the intervertebral disc (a fibrocartilaginous joint) and the paired facet (zygapophyseal) joints (synovial joints).

Location

Intervertebral joints are located between the vertebral bodies and between the superior and inferior articular processes of adjacent vertebrae, extending from the second cervical vertebra (C2) to the sacrum.

Types of Intervertebral Joints

1. Intervertebral Disc Joints (Between Vertebral Bodies)

• Joint type: Secondary cartilaginous joint (symphysis)
• Structure: Composed of an outer annulus fibrosus and inner nucleus pulposus
• Function: Acts as a shock absorber and allows limited movement between vertebral bodies

2. Zygapophyseal (Facet) Joints (Between Articular Processes)

• Joint type: Synovial plane joints
• Location: Between the inferior articular process of one vertebra and the superior articular process of the vertebra below
• Function: Allow gliding movements and contribute to spinal motion (flexion, extension, rotation)

Structure of the Intervertebral Disc

• Annulus fibrosus: Outer ring of fibrocartilage composed of concentric lamellae that resist torsion and tension
• Nucleus pulposus: Gel-like core that distributes compressive forces across the disc

Regional Variations

• Cervical region: Discs are thinner but more mobile; zygapophyseal joints are oriented obliquely to allow extensive motion
• Thoracic region: Discs are relatively thin; movement is limited due to rib attachments and facet orientation
• Lumbar region: Discs are thick and wedge-shaped; zygapophyseal joints are oriented to allow flexion-extension but resist rotation

Ligament Support

Intervertebral joints are supported by several key ligaments:

• Anterior longitudinal ligament: Runs along the anterior surface of vertebral bodies; prevents hyperextension
• Posterior longitudinal ligament: Runs along the posterior surface of vertebral bodies within the vertebral canal; limits flexion
• Ligamenta flava: Connect adjacent laminae; preserve upright posture and assist extension
• Interspinous ligaments: Connect spinous processes; limit flexion
• Supraspinous ligament: Runs along the tips of spinous processes; limits flexion
• Intertransverse ligaments: Connect adjacent transverse processes; limit lateral bending

Movements

Combined action of intervertebral discs and facet joints allows the spine to:

• Flex and extend
• Laterally flex (side bend)
• Rotate (especially in cervical and upper thoracic regions)

Innervation

• Zygapophyseal joints are innervated by the medial branches of the dorsal rami of spinal nerves
• Intervertebral discs receive sensory innervation from the sinuvertebral nerves (recurrent meningeal branches)

Clinical Relevance

• Degenerative disc disease: Age-related changes in the disc structure can lead to reduced disc height and pain
• Disc herniation: Nucleus pulposus protrudes through the annulus fibrosus, potentially compressing spinal nerves
• Facet joint osteoarthritis: Common cause of chronic back pain due to wear and tear of zygapophyseal joints
• Radiculopathy: Nerve root compression due to disc or joint pathology leads to pain, weakness, or numbness along the nerve distribution