Facet joint

facet joint
Anatomy
Humans have adapted to evolution in that they have gone from being a four-legged to a two-legged. This change has led to an adjustment of the facet joints to maintain their ability to stabilize and maintain the mobility of the forefoot segments. Worth knowing is that the facet joints are essentially sagittally oriented with an anterio-posterior direction the higher up the lumbar spine. This allows the vertebrae to:

Resist shear
Compression
torsional
In the lumbar spine, all facet joints are angled approximately 170 degrees to the vertical regardless of gender or ethnicity.

The structure of the joint
The facet joints are paired synovial joints which form the posterior joint mechanism between two adjacent vertebrae. Each joint is made up of a larger, posterior and medially directed concave joint surface starting from the lower vertebra, and an opposing smaller, anterior and laterally directed joint surface starting from the upper vertebra.

Innervation
The facet joints are innervated by a medial nerve from ramus dorsalis at the same level and with nerve branches from the level above. In the fibrous joint capsule around each joint, abundant nociceptive and autonomic nerve fibers are found. There are also nerve fibers in the synovial membrane but the function is not yet clear.

Lumbala facet members
The lumbar facet joint has a cartilaginous joint surface made up of hyaline cartilage, a synovial membrane and a fibrous capsule which restricts rotation around the joint shaft and prevents back sliding upon extension. The normal joint can hold between 1-2ml. You also have something similar to meniscus in the facet joint, which you believe will equalize anomalies in the cartilage.

Osteoarthritis and pain
The facet joint can often be a reason for back and leg pain. It has been discovered by anesthetizing the facet joint and thus has also been able to relieve back pain. It has been stated in various studies that between 15-45% is pain caused by the facet joint. However, the importance of facet joint degeneration for facet joint-triggered pain and low back pain is still being discussed today. The facet joint also constitutes a limitation of the spinal foramen and facet joint hypertrophy or a synovial cyst adjacent to the foramen can give rise to radicular pain (pain in the dermatoma of the nerve).

The facet joint can also be affected by osteoarthritis, just as it does in other cartilaginous joints. Cartilage erosions with the occurrence of subchondral sclerosis (densification of the underlying bone), hypertrophy and osteophyte formation can lead to narrowing of foramina and nerve compression as a result.

Osteoarthritis often also leads to changes in the joint capsule which in turn can affect the mobility of the joint. The incidence of osteoarthritis increases with the rising age and that it is mainly in the lumbar spine at level L4-L5 and in women you find osteoarthritis. Women are also more likely to have increased mobility in the lumbar segments, which is believed to be due to the sex hormone estrogen. The general view is also that disk degeneration precedes facet joint osteoarthritis.

Diagnostics
To diagnose the occurrence of facet joint osteoarthritis, the use of smooth X-rays, computed tomography and MRI examinations is used.

Plain X-ray
Relatively limited use if you do not take a picture with oblique projection.

Computer tomography
One cannot correlate the degree of facet joint pain to osteoarthritis changes.

MRI
One cannot correlate the degree of facet joint pain to osteoarthritis changes. One can see if there is an increased amount of fluid and thus suspect that there is an instability with increased sliding between the vertebrae at a flexion extension. This in turn may reveal a degenerative spondylolisthesis.