The facet joints connect the vertebra to one another. They are located at the back of the spine, and there are two facet joints between each pair of vertebrae, one one each side of the spine. The joints combine with the disc space, to create a three joint complex between every pair of vertebra. The facet joint has two bony surfaces with cartilage in between, and a surrounding joint capsule that contains synovial fluid. The cartilage and synovial fluid allow the joints of the spine to move with minimal friction.
What causes Facet Joint Arthritis
Facet joint arthritis is a type of osteoarthritis, and as with all osteoarthritis, the cartilage wears away with age, ultimately causing the facet joints to rub together, bone on bone, causing pain.
Being a synovial joint, the facet joints can also be affected by Rheumatoid Arthritis. People with rheumatoid arthritis will have inflammation of the synovial joints, and if this inflammation is not controlled, it erodes first the cartilage, then the bone. The end result is loss of motion, stiffness and potentially severe back pain. The loss of cartilage is termed osteoarthritis, but the root cause of the cartilage loss is not age and wear and tear, but the inflammation of rheumatoid arthritis.
Most commonly, the facet joints degrade in the lumbar spine. But facet joint arthritis can affect any part of the spine, and the cervical spine is also often affected, resulting in neck pain, stiffness and loss of motion.
Symptoms of Facet Joint Arthritis
Most people will experience low back that becomes worse when twisting, standing or bending. Often the pain is confined to one area of the spine, but it’s also possible that many levels of facet joints are affected, causing pain in many areas. However, there is usually no nerve entrapment or radiating pain into the legs or buttocks, numbness or sciatica, as can happen with herniated discs.
As the facet joints degenerate, they develop bone spurs (osteophytes), which causes narrowing of the space available for the nerve roots to exit the spinal canal, which contributes to spinal stenosis.
It is also common for people who have facet joint arthritis to have degenerative disc disease, which can also contribute to the pain.
Because of the complex structures of the spine, and many potential causes of pain, diagnosing exactly where the pain is coming from can be a challenging process.
How is Facet Joint Arthritis Diagnosed?
MRI is a good option for diagnosing the source of lower back pain, as it can also show degenerating or herniated discs, spinal alignment, nerve impingement or even abdominal problems that could be mimicking back pain.
If the facet joints are degenerating from arthritis, the MRI will show the severity, although this doesn’t always correspond to the degree of pain the patient may feel.
The most definitive way to discover if back pain is originating from the facet joints is to perform a facet joint injection, in which the suspected facet joints are injected with local anaesthetic and cortisone. The patient will feel immediate relief from the anaesthetic, if the facet joints are the problem, and more extended relief in a 3-5 days from the cortisone.
If the patient doesn’t experience pain relief, then the facet joints are not the cause of pain.