Up to an astonishing 90% of people will experience low back pain at some time in their lives. According to the National Center for Health Statistics, over 14% of new visits to primary care physicians are for low back pain. Spine pain secondary to degenerative disc disease most often affects young to middle-aged people with peak incidence at around 40 years old. However, I have seen teenagers with significant degenerative disc disease. Factors such as genetics, trauma, and environment can contribute to an earlier presentation. And of course, radiologic evidence of disc disease increases with age to nearly 100% by age 60. However, not all degenerative discs are painful.
As we age, we endure both macrotraumas and repetitive microtraumas and undergo changes in body habitus that alter and redistribute biomechanical forces unevenly on the lumbar spine. Much like your knee, the padding or cartilage is mostly water-based and will progressively degenerate the longer we spend in gravity. Factors such as weight, nutrition, genetics, trauma (macro or repetitive micro), and environment may contribute to accelerated degeneration. This degeneration of the lumbar segment progresses with age with characteristic anatomic, biomechanical, radiologic, and clinical findings and is called degenerative disc disease.
Two of the most common pain generators in the lumbar spine that result from this degeneration are 1) the disc, and 2) the facet joints, with facet mediated pain being more common the older you get, and discogenic pain being more common overall. Strong experimental evidence suggests that most episodes of low back pain are a consequence of disc injury, rather than muscle/tendon/ligament strain. Most people know that the disc can bulge out and hit a leg nerve, causing sciatica; but, the disc itself has nerve endings, and tears in the disc from degeneration can cause significant back pain. This is referred to as Discogenic Pain.
The patient’s history and exam help rule out other reasons for back pain. With pressures within the disc increasing significantly with forward flexion at the waist, patients will typically report exacerbation of pain with prolonged sitting, driving, rising from a seated position, first thing in the morning, bending over to pick something up, tie their shoes, doing dishes, bending over to shave, etc. However, the discs bear some amount of pressure in all positions, so there is some variability. Often there is a specific trauma: I’ve heard coughing, sneezing, vomiting, picking up a table, picking up something as light as a pen. However, just as often, there is no inciting event and patients will “wake up with it.” Relieving positions often include lying flat or on side with legs bent up, sort of in the fetal position. Staying active and moving around is often reported to ease discomfort. Often patients will point to the lumbar spine and report pain in a band-like pattern around the waist line and radiating into hips. My first clue to discogenic pain begins with my first view of the patient as I walk into the room. Patients with discogenic pain may prefer to stand or pace around the room. If seated, they may recline back to one side to relieve the pressure.
Imaging findings are matched to the patient’s history and exam. MRI at this stage may reveal desiccation (dehydration, or a “dark disc”), disc bulging, or a “high-intensity zone (HIZ)” or tear in the annulus.
Treatment always begins with a discussion on ergonomics and a preventative home exercise program, with an emphasis on core strengthening and lumbar stabilization. Medications can include both steroidal and non-steroidal anti-inflammatories and muscle relaxants. Physical therapy and/or chiropractic manipulation to include traction and decompression may help with symptoms as well. Cortisone injections using live x-ray and moderate sedation can alleviate pain by decreasing inflammation if symptoms persist.
by Nathan S. Walters, MD
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