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As a rule, there are three (3) joints at each segmental joint level of the spine.
- one anterior, midline disc joint
- two, paired left and right, posterior facet joints
- Disc joint:
- amphiarthrotic cartilaginous joint
- united by fibrocartilage, with outer annulus fibrosus fibers and an inner nucleus pulposus.
- Facet joints
- planar/gliding diarthrotic synovial nonaxial joints.
- united by the bilayer outer fibrous membrane and inner synovial membrane
Joints of the spine – posterior view – drawn anatomy
- Generally, facet joints determine the type of motion best afforded at that joint level.
- Disc joints (depending on how thick they are) determine how much motion is afforded at that level.
Note: Facet joints are also known as zygapophyseal joints (Z-joints).
