The facet joints are the smooth, flat surfaces of the vertebrae that interlock and allow the spine to flex yet still maintain its stability. The facet joints permit gliding movements between the vertebrae. There are two facet joints between each vertebrae located on each side of the vertebrae. Facet disease can occur at any level of the spine, but is most common in the lower back (lumbar) region. There are a number of terms that are used to diagnose facet problems such as facet arthritis, facet joint syndrome, facet disease, facet hypertrophy and degenerative facet joints. In general, all of the terms mean pretty much the same thing—arthritis or degeneration of the facet joint.
Facet disease is caused by the cartilage in the joints being worn down as a result of wear and tear, aging, injury or misuse. Another cause of facet disease is spondylolisthesis, which is when one vertebra, usually in the lumbar spine, slips forward over the lower vertebra

When the facet joints become inflamed due to injury or age the result is stiffness and/or pain. As the facet joints deteriorate, they also might not align properly which can cause pain. Additionally, rubbing on the joints wears out the cartilage and fluid that lubricates them. As a result, bone can rub on bone, which results in painful back problems.

The facets are compressed when an individual leans backward or to the side, so someone with a facet problem would more than likely feel pain in those positions. Leaning to the front reduces the stress on the facets, so a person with a facet problem would probably find relief in that position. Some experts believe that facet pain can weaken the muscles that help to strengthen the spine, which can lead to instability. Among the problems that affect facets are facet syndrome, facet disease and facet arthritis.