Facet joint

Last revised by Anthony Liu on 21 Dec 2023

Facet joints, also known as apophyseal or zygapophyseal joints, are the synovial articulations of the posterior arch of the vertebrae and form part of the posterior column. 

They are symmetrical synovial-lined joints with a fibrous capsule that connect the articular facets of the vertebrae. The facet joints are situated between the pedicle and lamina of the same vertebra and form the articular pillars that act to provide structural stability to the vertebral column as a whole.

The facet joints are formed by two articular processes of adjacent vertebrae, with the superior articular process of one vertebra located immediately anterior to the inferior articular process of the vertebra above. The facets joints however do demonstrate some regional variation in orientation and morphology:

  • cervical spine

    • oriented in the coronal plane so best viewed in the axial and sagittal planes

    • in the sagittal plane, the facet joints slope from anterosuperior to posteroinferior

  • thoracic spine

    • oriented in the coronal plane so best viewed in the axial and sagittal planes

    • in the sagittal plane, the facet joints lie almost vertically

  • lumbar spine

    • oriented in the sagittal plane with curved joint surfaces so best viewed in the axial plane

    • lumbar facet joints are critical stabilizers of the motion segment preventing translation and excessive amounts of rotation and flexion

  • ~ 33 % of dynamic compressive load and 35 % of static load may be sustained by lumbar facet joints 3

Variation in the orientation of the two facet joints at the same level is not uncommon and known as facet joint tropism.

The facet joints kept fixed in position by the posterior ligamentous complex.

Pain sensation of the facet joint capsule and synovial folds is provided by the medial branch of the dorsal ramus 3. Each medial branch innervates the facet joint of its level and the facet joint below (e.g. the L1 medial branch innervates the L1/2 and L2/3 facet joints) 5, knowledge of which is important when performing medial branch blocks and ablations.

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