What is Facet Joint Hypertrophy?

Spinal Arthritis and Spondylosis

Depiction of a spine with spondylosis and facet joint hypertrophy
Facet joint hypertrophy may cause radiculopathy symptoms. Medical Art Inc./E+/Getty Images

What is Facet Joint Hypertrophy?

Facet hypertrophy is an age-related type of spondylosis (spondylosis is a general term meaning degenerative changes in the spine,) in which enlargement of the facet joints occur. (Hypertrophy refers to getting bigger, or enlargement.)

Facet Joint Angles Determine Spinal Flexibility

Facet joints, which are more technically named zygapophyseal joints, are the angled joints located on either side of the bony ring that is in back of the vertebral bodies.

 Facet joints help stabilize movement of your spine.  Their angle and the height of the intervertebral disc located at the same spinal segment determines the parameters of the movement that are allowed at that joint.  This means that for each region (i.e., cervical, or neck, thoracic, or upper and mid-back, and lumbar, or low back) the amount of flexibility and the direction in which you can take your spine differs.

For example, in the cervical spine the facet joints are angled at about 45 degrees, which allows for movements in all directions:  Flexion, or forward bending, or backward bending, lateral flexion, or side bending and rotation, or twisting.)

In the thoracic region, which corresponds to your upper and mid-back areas, the facet joints are angled at about 60 degrees.  This permits side bending and twisting but no flexion or extension.

And finally, in the lumbar spine, the facet joints are positioned at a 90-degree angle (approximately) allowing for only forward or backward bending of the spine.

  This, either in addition to, or rather than, very tight back muscles may be why you feel inflexible in your low back (if you do.)

Age Related Wear and Tear of Facet Joints

Facet joints are synovial joints complete with a surrounding capsule and an inner self-lubricating capacity.  Because of this type of structure, normal, healthy facet joints tend to glide easily and smoothly without causing you pain.

 

But especially as we age, this area is prone to wear and tear. In fact, some degree of wear and tear of facet joints cannot be avoided – it probably occurs in anyone who gets old enough, although it may not cause problems. Symptomatic facet joint arthropathy is not inevitable for all people, even those who live into the 90s and 100s.

Over time, wear and tear erodes the cushioning in between the two bony surfaces of the facet joint, eventually leaving you with bone on bone contact during spinal movement.  As the two bony surfaces of the joint rub against one another, the area becomes inflamed, which in turn stimulates new bone growth and bone spurs.  This may be called by a number of names: Spondylosis, spinal arthritis, and facet joint syndrome.

The new bone that is laid down may become larger than the original it is replacing and at that point, the condition moves from being called facet joint syndrome to facet joint hypertrophy.  (It's still called spondylosis and/or spinal arthritis.)

Facet Joint Related Cervical Radiculopathy

The facet joints are very close to the intervertebral foramen, which is the “hole” on either side of the spine through which spinal nerve roots pass on their way out to all parts of the body.  When you have facet joint hypertrophy, not only might you experience pain and/or irritation at the joint, but the enlargement may encroach on and narrow the foramen.  In this case, the nerve material may possibly “bump into” the bone spur that has been laid down during the arthritic process described above.  When this occurs, you may experience cervical radiculopathy, which is a collection of signs and symptoms that can include pain and/or pins and needles down your arm as well as other things.

Depending on your symptoms and the region of your facet joint hypertrophy, the ICD-10 code (code used for insurance billing insurance) for facet joint hypertrophy may be M47.

Sources:

Caridi, John, M., M.D., Pumberger, Matthais, M.D. Hughes, Alexander, P., M.D. Cervical Radiculopathy: A Review. Hospital for Special Surgery Journal. 2011.

Ferrara, Lisa A., Review Article, The Biomechanics of Cervical Spondylosis. Advances in Orthopedics Volume 2012. Hindawi Publishing Corporation. Accessed November 2015.

Mullin, Jeffrey, Shedid, Daniel, Benzel, Edward. Overview of Cervical Spondylosis Pathophysicology and Biomechanics. World Spinal Column Journal. September 2011.

Spondylosis M47. IDC10Data.com Accessed November 2015.

Lowe, R., Ritchie, R., Sareen, A. Facet Joints. Physiopedia. Accessed: November 2015.

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