The motion segment between two vertebrae is formed by the intervertebral disc at the front and the 2 facet joints at the back. The disc is a special fibrous joint and is quite different to the common synovial joints that join the bones of the skeleton. The facet joints are much like the other common synovial joints in the body. The surfaces of the bones are capped by a smooth glistening articular cartilage and there is a capsule of fibrous tissue that contains the joint and an inner membrane that makes fluid to lubricate the joint.
Facet joints are therefore prone to the same conditions that affect the other synovial joints. Like the knee and the hip and the finger joints, facet joints can develop both wear and tear (degenerate) osteoarthritis and can be affected by inflammatory conditions of the joints like rheumatoid arthritis.
All synovial joints degenerate with age. Some joints , like the weight bearing joints of the hip and knee, seem to wear earlier than other joints. The facet joints of the spine take more load as we age because the discs are also degenerating and as they lose hydration and height the facet joints have to take more load. This is most common in the lower segments of the lumbar spine where the loads are greatest.
Whilst facet joint arthritis is quite common on imaging studies of older spines, it does not seem to be painful for most people. When it does cause pain and stiffness the symptoms seem to be worse in an extended spine position (ie bending backward) where the facet joints are loaded. Relief is achieved in a flexed spine position (ie bending forward). It is uncommon to find patients with a pure extension pattern pain (<10% of all back pain) and most commonly facet arthritis is not the dominant pain generator, but can be part of the reason for back pain.
Treatment for facet arthritis should be directed at reducing the load across the joint with appropriate exercises that strengthen the muscles that can help share the load. Core muscle strengthening and control exercises are most commonly prescribed. Facet joint blocks or cortisone injections can also help to reduce the pain from arthritis for a few weeks to months but should be combined with the exercise regime to maximise results. More recently radiofrequency dennervation of the facet joints has been used to reduce facet joint pain and for some people they seem to help for months to a year or so.
Surgery for painful isolated facet joint arthritis is not usually indicated. However, facet arthritis can be complicated by spinal stenosis or spondylolisthesis and surgery will be indicated if the stenosis and symptoms are severe enough.