Facet joints safely guide and control the movement of spinal bones. They provide stability to the spinal column whilst allowing movement. They are hinge-like, connect vertebrae and are found at the back of the spine.
In the spine, facet joints regulate the movement of the bones by functioning like a door and a doorstop. For example, it is facet joints that stop backward movement when bending. They are located at all spine levels except on top of the cervical spine and are covered by facet joint capsules. The facet joint capsules contain a fluid that lubricates and protects the joints. The anterior disc space works with the posterior paired facet joints, creating a three-joint complex at each level of the spine. The complex allows extension/flexion, lateral and rotational bending.
The surfaces of facet joints are relatively hard, thick and slick when healthy. But if the joints are injured, irritated or rarely used, the joint surfaces become softer, thinner and almost sticky making movement difficult or painful. Moreover, since facet joints are usually in constant movement, they normally become degenerated or wear out. When this happens, the cartilage may disappear or become thin and a reaction of the bone under the joint can occur leading to enlarged joints and overgrowth of bone spurs. This condition is very painful and may require surgical intervention.