What are facet joints and how do they function?

The spine is a collection of connected joints, with the facet joints, or zygapophyseal joints, making your back flexible and enabling you to bend and twist. Back pain is usually caused by Facet Joint Syndrome, sometimes known as Facet Joint Sprain and obviously involves the facet joints, the small stabilising linkages found between and behind adjacent vertebrae. There are two joints in every vertebra, one on either side of the spine.
Nerve signals leave your spinal cord through these facet joints and travel to other parts of your body. In a healthy state your facet joints – classified as synovial joints – are coated with hyaline cartilage, which causes your vertebrae to slide smoothly against each other without grating or grinding.
The facet joints are also contained within a joint capsule awash with synovial fluid and all of these protections allow the joint to provide stability for the spine and control excessive movement, especially in rotation and extension.