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Facet joint of vertebra (Zygapophyseal joints)

The facet joint, also known as the zygapophyseal joint, is a synovial articulation between the superior articular process of one vertebra and the inferior articular process of the vertebra above it. These paired joints are located posterolaterally on each vertebra, forming part of the posterior vertebral arch. Facet joints are lined with hyaline cartilage, enclosed by a fibrous capsule, and contain a small synovial cavity with fluid, allowing smooth articulation.

Facet joints guide and restrict spinal motion, providing flexion, extension, rotation, and lateral bending while preventing excessive movements that could compromise spinal stability. They bear up to 20–30% of axial load in the lumbar spine, with contribution varying by spinal level. Degeneration, osteoarthritis, or trauma can lead to facet hypertrophy, joint space narrowing, and pain syndromes, making accurate imaging essential for diagnosis and surgical planning.

Function

  • Facilitate controlled spinal motion (flexion, extension, rotation, lateral bending)

  • Provide posterior stability to the vertebral column

  • Limit excessive spinal movement, protecting intervertebral discs and spinal cord

  • Distribute axial load, particularly in the lumbar spine

  • Serve as a landmark for spinal interventions such as facet injections or radiofrequency ablation

Synonyms

  • Zygapophyseal joint

  • Apophyseal joint

  • Posterior intervertebral joint

MRI Appearance

T1-weighted images:

  • Facet joint space appears as a narrow line of low signal intensity (hypointense), representing articular cartilage

  • Surrounding cortical bone of the superior and inferior articular processes is low signal

  • Marrow within articular processes is high signal, providing natural contrast

  • Degenerative changes (osteophytes, sclerosis, or synovial cysts) appear as altered signal

T2-weighted images:

  • Facet joint cartilage remains low signal intensity (hypointense)

  • Synovial fluid within the joint cavity is high signal (hyperintense), delineating the joint space

  • Joint effusion, inflammation, or cysts appear hyperintense, highlighting pathology

STIR (Short Tau Inversion Recovery):

  • Cortical bone of articular processes remains low signal

  • Bone marrow edema, inflammation, or facet joint effusion appears hyperintense, useful for acute injury, arthritis, or infection

T1 Post-Contrast (Gadolinium-enhanced):

  • Normal facet joint capsule may show minimal enhancement due to vascularized synovium

  • Pathological conditions (synovitis, inflammation, infection, or cysts) demonstrate enhancement along the capsule or within the joint space

CT Appearance:

  • Facet joints appear as articulating bony surfaces with clear joint space

  • Cortical bone is hyperdense, trabecular bone slightly lower in density

  • Degenerative changes such as osteophytes, joint space narrowing, subchondral sclerosis, and cysts are well visualized

  • Excellent for evaluating posterior spinal alignment, facet tropism, and surgical planning

MRI images

facet joint of of vertebra mri axial image -img-00000-00000_00001

MRI images

Facet joint of vertebra (Zygapophyseal joints) mri sagittal image -img-00000-00000

CT image

Facet joints of vertebrae ct axial image

CT 3D VRT image

Facet joints of vertebrae ct 3d image