Arthritis is the most common cause of low back pain, especially in people over age 50. The low back contains five sets of facet joints, one on the left and one on the right side of each spinal bone. Like joints in any other part of the body the low back facet joints can be injured, or become inflamed.

See Lumbar Spine Anatomy and Pain

Quick Definition of Spinal Arthritis

The word arthritis comes from a combination of the Greek "arthros," meaning a joint and "-itis," meaning inflammation. The facets are the only joints in the spine. Spinal arthritis therefore means inflammation of the spinal facet joints.

Watch: Facet Joint Anatomy Animation

Causes of Arthritis in the Lower Back

Arthritis of the spine usually occurs due to internal damage to the facet joints. The surfaces of the facet joints are lined with smooth cartilage to allow for movement as the two sides of the joint rub against one another. However, the joint can become painful through the following process:

See Treatment Options for Facet Joint Disorders

The spinal facet joints in the lower back are prone to developing osteoarthritis. The joints are quite small compared to the amount of body weight they bear. The resulting stress and strain makes them susceptible to damage to the cartilage, and injury. The accumulation of injuries over a lifetime causes the joints to break down, or degenerate.

See Facet Joint Osteoarthritis

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Facet joint breakdown also comes as a result of torn discs. Discs act as shock absorbers for the spine. They have a tough outer part, and a soft inner part. The soft inner part absorbs the shock. But the hard outer part can tear due to degeneration or even injury. The torn discs don’t absorb stress and strain very well, which leads to excessive force being transmitted to the facet joints.

See Diagnosing Disc Problems

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The degenerative process is similar to what happens in a car. If the shocks go out and aren’t replaced, the next thing that happens is the springs break. In the lower back, once the torn disc stops absorbing the stresses and strain of everyday life, the facet joints go out next. Once the facet joints are injured they become inflamed, swell, cause muscle spasm, and the back pain cycle begins.

See How a Disc Becomes Painful

Dr. Daniel Lieberman is a neurosurgeon and founder of Phoenix Spine & Joint. He specializes in spine surgery and has more than 15 years of clinical experience. In addition to providing spine care, Dr. Lieberman has served as Adjunct Faculty at the Biodesign Institute of Arizona State University.

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