Medical Media Images

Thursday, June 12, 2014

What is a "Facet Joint"? Shown and Explained with Color X-Ray and Color MRI Images

The Facet Joints of the Spine are small Motion Joints located on the back of the Spine. Their job is to guide and limit the motion of the Spine. Our Spine consists of many "motion segments" which give us our overall mobility. Each "motions segment" consists of a Spinal Disc in the front of the Spine and two Facet Joints on the back of the Spine. Without the Facet Joints, the Spine would move in all directions equally well. However that would be too much motion which would put our Nerve Supply at risk. The Spinal Cord and Spinal Nerves are located within a large tube (Spinal Canal) at the center of the Spine. If Vertebrae could move too much, the Spinal Cord and Nerves would be stretched and twisted which they cannot tolerate. So, this is where the Facet Joints come in. They control the motion of the Spine, only allowing a certain degree which is safe for the rest of the Spine's Anatomy.

Lets take a look at a Color X-Ray which shows the Facet Joints of the Low Back (Lumbar Spine). The black arrows point to some of the Facet Joints. Not all Joints can be seen on a straight-on (AP) X-Ray of the Low Back. This Image is Interactive. As you move your mouse cursor over the Image, the Interactive Tags appear. Each Tag displays text to explain a specific part of the Anatomy.

AP Color X-Ray of the Lumbar Spine Facet Joints
Interactive Image. If the tags do not display correctly due to slow Browser Speed, just reload the Image.

The next Image is of the Facet Joints is from a slightly different position. This Color X-Ray is taken from an angle (about 45 degrees). With this type of X-Ray view (Oblique), the Facet Joints open wider, since their orientation is angled. The green arrows point at the Facet Joints of the Low Back.

Oblique Lumbar Spine Color X-Ray of the Lumbar Facet Joints

To get a better 3-Dimensional idea about the Facet Joints, lets take a look at a Color MRI of the Low Back (Lumbar Spine). This perspective is a horizontal slice across the Low Back. The Orientation Box on the whole-body Color MRI on the left, shows you where the slice is taken from. Notice how close the Spinal Disc and Facet Joints are to each other. The Spinal Nerves (yellow) travel right between them. So, if either a Spinal Disc becomes larger (herniates) or a Facet Joint develops Bone Spurs, the Spinal Nerves can become trapped. This is called "Sciatica" (spinal nerve pain in the leg).This Image is also Interactive.

Axial Lumbar Spine Color MRI Lumbar Spine Anatomy
Interactive Image. If the tags do not display due to slow Browser Speed, just reload the Image
Now lets take a look at Facet Joints which have degenerated. This next Interactive Color MRI shows you how different degenerated (arthritic) Facet Joints look from Normal ones. The red arrows point at the bone spurs which have developed as part of the degeneration. The Joint itself has become narrow as the Cartilage has worn off. This is also an Interactive Image.

Axial Color MRI of Lumbar Spine Facet Joint Arthritis Degeneration

Facet Joints in the low back are a common cause of Back Pain. Pioneers in Medicine first discovered the Facet Joints as the primary source of Back Pain and Sciatica. However, eventually, the Spinal Disc received more attention. In recent years, the Facet Joints have been given a higher priority as culprits of low Back Pain. This has lead to new interventions, including new types of Surgeries.

In our next Blog, we will discuss the Treatments for low Back Pain from Facet Arthritis. Stay tuned!
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