The Zygapophyseal (Facet) Joints and the Capsular Ligaments of the Spine

An official anatomical term, "zygapophyseal joint," is difficult to pronounce and remember. Therefore it is universally substituted by the more convenient terms like "Z-joints" or "facet joints." We use the terms "zygapophyseal joints" and "facet joints" as synonyms on this website.

The zygapophyseal joints are the classical synovial joints (with the articular surfaces covered with cartilage, with articular gap and synovial cavity hermetically surrounded by the capsule) localized between the articulatory processes of adjacent vertebrae. The capsular ligaments of the facet joints consist of the fibers oriented more or less perpendicular to the joint line1 and look like thin ligaments. Their primary function is to seal the articulation itself. However, the strength of the capsular ligaments is on par with the other major spinal ligaments like the yellow and interspinal ligaments2.


  • 1Bogduk N. Clinical Anatotmy of the Lumbar Spine and Sacrum. 4th ed, Elsevier Churchill Livingstone, 2005, p.33
  • 2White, A. A. & Panjabi, M. M. Clinical Biomechanics of the Spine. Lippincott Williams & Wilkins, 1990; p.22

  • Icon of crossfade image Cervical spine with the capsular ligaments of the facet joints
    Cervical spine, demonstrating the zygapophyseal (facet) joints Cervical spine with the capsular ligaments of the facet joints
    The cervical spine. Posterior and lateral view. Click an image to see the capsular ligaments of the zygapophyseal (facet) joints.
    The shape of the facet articulatory surfaces is almost flat at that level, and the orientation of the facet joint is oblique. This shape and orientation cause strong coupling of lateral bending with axial rotatory motions. I.e., the lateral flexion of the cervical spine (within the C2–C7) is invariantly associated with the axial rotation of involved vertebrae, and vice versa – the axial rotation of the neck is coupled with the lateral bending of cervical vertebrae*.
  • *Lysell, E. Motion in the cervical spine. An experimental study on autopsy specimens. Acta orthopaedica Scandinavica, 1969, Suppl.123:1

  • Icon of crossfade image Upper thoracic spine with the capsular ligaments surrounding the facet joints
    Upper thoracic spine posterior and side view, demonstrating the facet joints Upper thoracic spine with the capsular ligaments surrounding the facet joints
    The upper thoracic spine. Posterior and lateral view. Click an image to see the capsular ligaments.
    The shape of the articulatory surfaces of the facet joints at that level remains flat. However, the facets are oriented more vertically compared to the cervical level and approach the frontal plane. This shape and orientation restrict the motion in the sagittal plane that makes the thoracic the most rigid part of the spine in terms of the range of the flexion/extension motions*.
  • *Lewandowski J. Kształtowanie się krzywizn fizjologicznych i zakresów ruchomości odcinkowej kręgosłupa człowieka w wieku 3–25 lat w obrazie elektrogoniometrycznym. Poznan; 2006.

  • Icon of crossfade image Lower thoracic and upper lumbar spine (thoracolumbar transition zone), demonstrating the orientation of the articulatory facets of the zygapophyseal joint
    Lower thoracic and upper lumbar spine (thoracolumbar transition zone), demonstrating the orientation of the articulatory facets of the zygapophyseal joint Lower thoracic and upper lumbar spine (thoracolumbar transition zone), with the capsules of the zygapophyseal joint
    The lower thoracic spine. The thoraco-lumbar transiotion zone. Posterior and lateral view. Click an image to see the capsular ligaments.
    The lower thoracic spine's peculiarity is the facet joint plane orientation transition from the more or less frontal (above the Th11) to the predominantly sagittal (lumbar spine). This transition reflects the shift from the rotation-oriented (thoracic) to the more flexion/extension-oriented part of the spine (lumbar)*.
  • * Hsu CJ, et al. Measurement of spinal range of motion in healthy individuals using an electromagnetic tracking device. J. Neurosurg. Spine, 2008, 8:135–142.

  • Icon of crossfade image Facet joints of the lumbar spine. Posterior and lageral view
    Capsular ligaments of the lumbar spine. Posterior and lateral view Facet joints of the lumbar spine. Posterior and lateral view
    The lumbar spine. Posterior and lateral view. Click an image to see the capsular ligaments.
    The shape of the articulatory surfaces of the lumbar spine is slightly rounded. Still, the facet's orientation is predominantly sagittal, facilitating the lumbar spine flexion & extension motion. On the other hand, this shape and orientation restricts the rotatory movements, making the lumbar spine the most rigid part of the spine in terms of the axial rotation1,2.
  • 1 Lewandowski J. Kształtowanie się krzywizn fizjologicznych i zakresów ruchomości odcinkowej kręgosłupa człowieka w wieku 3–25 lat w obrazie elektrogoniometrycznym. Poznan; 2006.
  • 2 Kapandji A. The Physiology of the Joints. Vol 3. The Trunk and the Vertebral Column. 2nd ed. (Livingstone C, ed.). 1974.
  • Published: 09/Sep/2021