Facet joints (also known as the Zygapophysial joints or Z-joints) are paired structures at the back of each vertebra (spinal column bones). The facet joints, like other joints in the body, form a working motion unit that allows movement between two vertebrae.

The term “lumbar” refers to the lower part of the back. Similar to the shoulder or knee joints, lumbar facet joints are surrounded by a capsule that bathes the moving parts in lubricating fluid.