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Zygapophyseal joint

The zygapophyseal joint, commonly called the facet joint, is a paired synovial joint formed between the superior and inferior articular processes of adjacent vertebrae. These joints are present at every vertebral level from the cervical spine to the lumbar spine and play a major role in guiding spinal motion and maintaining segmental stability.

Zygapophyseal joints are key anatomical landmarks in spinal anatomy and are routinely evaluated in radiography, CT, and MRI for alignment, morphology, and joint integrity.

Synonyms

  • Facet joint

  • Apophyseal joint

Location

  • Located posterior to the vertebral body and intervertebral disc

  • Formed between the inferior articular process of the vertebra above and the superior articular process of the vertebra below

  • Present bilaterally at each motion segment

  • Orientation varies by region:

    • Cervical: oblique

    • Thoracic: coronal

    • Lumbar: sagittal

Anatomical components

  • Articular processes:

    • Superior articular process

    • Inferior articular process

  • Articular cartilage:

    • Hyaline cartilage covering joint surfaces

  • Joint capsule:

    • Fibrous capsule enclosing the synovial cavity

  • Synovial membrane:

    • Lines the inner surface of the capsule

  • Joint cavity:

    • Contains a small amount of synovial fluid

Relations

Anteriorly:

  • Pedicle and vertebral body

  • Intervertebral disc (indirect relationship)

Posteriorly:

  • Paraspinal muscles

  • Lamina and spinous process

Medially:

  • Spinal canal

  • Ligamentum flavum

Laterally:

  • Intervertebral foramen

  • Exiting spinal nerve root

Superiorly:

  • Superior articular process of the lower vertebra

Inferiorly:

  • Inferior articular process of the upper vertebra

Structures related to the zygapophyseal joint

  • Joint capsule and synovium

  • Ligamentum flavum (medial)

  • Paraspinal muscles (posterior)

  • Nerve root in the adjacent neural foramen

X-ray appearance

Spine radiographs (AP, lateral, oblique views):

  • Facet joints: Visualized best on oblique views as the “Scotty dog” appearance in the lumbar spine

  • Joint space: Narrow linear radiolucent gap between articular processes

  • Articular surfaces: Smooth cortical margins

  • Alignment: Symmetric bilateral joint orientation

CT appearance (pre-contrast)

Non-contrast CT:

  • Articular processes: Well-defined cortical bone with trabecular interior

  • Joint space: Thin hypodense cleft between opposing articular surfaces

  • Orientation: Clearly demonstrates regional facet orientation

  • Capsule: Usually not separately visualized

  • Utility: Excellent for depicting bony morphology and joint congruity

MRI appearance

T1-weighted images:

  • Articular bone marrow: Intermediate-to-high signal in cancellous bone

  • Cortical margins: Low signal intensity

  • Joint space: Low-signal linear cleft

  • Capsule: Thin low-signal rim

T2-weighted images:

  • Joint fluid: High signal within the synovial cavity

  • Articular cartilage: Intermediate signal lining joint surfaces

  • Surrounding soft tissues: Intermediate-to-high signal

STIR:

  • Joint cavity: High signal from synovial fluid

  • Periarticular soft tissues: Intermediate-to-high signal

  • Bone marrow: Uniform low-to-intermediate signal in normal marrow

MRI image

zygapophyseal joint of vertebra , Location and Imaging Appearance -img-00000-00000_00001

MRI image

zygapophyseal joint of vertebra , Location and Imaging Appearance -img-00000-00000_00002

CT image

zygapophyseal joint of vertebra , Location and Imaging Appearance -img-00000-00000

X Ray image

X Ray Zygapophyseal joint