Zygapophysialis

Zygapophysialis is an anatomical term used to designate features of the zygapophysial joints, or facet joints, of the vertebral column. Zygapophysial joints are synovial, planar joints that contribute to the articulation between adjacent vertebrae and help control spinal motion and stability.

Each zygapophysial joint is formed by the articulation between the superior articular facet of a vertebra and the inferior articular facet of the vertebra above it. The joints are enclosed by a fibrous capsule lined with synovial membrane and reinforced by ligaments. They are innervated by the medial branches of the dorsal rami, which provides sensory input related to pain and proprioception.

The orientation of the facet joints varies along the spine and influences movement. In the cervical region, the facets are oriented obliquely and permit a combination of flexion, extension, and rotation. In the thoracic region, they are oriented more coronally, which limits rotation. In the lumbar region, they are oriented sagittally, facilitating flexion and extension with more constraint on rotation.

Functionally, the zygapophysial joints contribute to spinal stability, load distribution, and guided motion between vertebrae. Clinically, degenerative changes can lead to facet arthropathy or facet joint pain (facet syndrome). Imaging of the joints and targeted facet joint injections are common tools for diagnosis and management of facet-related pain.