Spine Anatomy and Osteoarthritis

The spine is made up of 33 vertebral bones stacked on top of each other. The vertebrae of the spine are not uniform; rather, the shape of each vertebra changes slightly, one by one, from the top to the bottom. The vertebrae meet at varying angles, so the spine has natural curves.

Vertebrae are separated by vertebral discs, which provide cushion and reduce friction. The bones are connected by muscle and ligaments but the main stabilizing structures are the disc and the 2 facet joints (right and left). The spine’s vertebrae, facet joints, vertebral discs, and surrounding soft tissue (e.g. muscles and ligaments) are highly interdependent.

The disc-facet complexes are the "joints" or mobile segments of the spine. Mobile segments are at risk for degeneration and may be a source of pain.

See Understanding Joint Pain

Spine Alignment and Degeneration

How the spine is aligned and how weight is distributed along the spine can affect the development of osteoarthritis, for example:

• Poor posture, such as hunching the neck and upper back, puts facet joints into unnatural angles and strains muscles and other soft tissue. Chronic poor posture increases the likelihood of osteoarthritic joint degeneration as well as other degenerative changes in the spine.
• When a vertebral disc deteriorates, the nearby facet joints may be forced to bear twice as much weight as normal.¹Dunlop, R.B., Adams, M.A. & Hutton, W.C. Disc space narrowing and the lumbar facet joints. J. Bone Joint Surg. Br. 66, 706-710 (1984).^,2Adams, M.A. & Hutton, W.C. The mechanical function of the lumbar apophyseal joints. Spine (Philia Pa 1976) 8. 327-330 (1983).^,3Gellhorn AC, Katz JN, Suri P. Osteoarthritis of the spine: the facet joints. Nat Rev Rheumatol. 2012 Nov 13. doi: 10.1038/nrrheum.2012.199. [Epub ahead of print] PubMed PMID: 23147891. In turn, the facet joints may be more prone to more wear and tear, resulting in osteoarthritis.

  See What Is Osteoarthritis?

Because of the interdependence of all spinal structures, it is common for one degenerative spinal condition, such as arthritis, to be accompanied by other degenerative changes in the spine.

For example, a patient with painful symptoms from osteoarthritis may also present with radiculopathy or leg pain from lumbar degenerated discs and spinal stenosis.

See How Osteoarthritis Can Lead to Spinal Stenosis

Certain Facet Joints Are More Prone to Osteoarthritis

Doctors have found that certain segments of the back are more prone to osteoarthritis:

• In the lower back, osteoarthritis is most common between the L4-L5 vertebrae, followed by L5-S1.
• In the cervical spine, osteoarthritis seems to be most common between the C4-C7 vertebral segments.

Segments in the middle of the back, called the thoracic spine, have less motion, because of the rib cage, and are thus not prone to developing osteoarthritis, though it is possible.

Early Treatment Can Reduce Pain

Chronic neck or back pain should not be ignored. Pain and other symptoms may worsen without treatment. Patients who understand the symptoms and causes of spinal osteoarthritis, get an accurate diagnosis, and follow an appropriate treatment program, can encourage healthy joint function and minimize the progression of symptoms.

As a general rule, the earlier a patient receives treatment, the less likely he or she will experience complications down the road.

Read more about Arthritis Treatment Options