Pain Generators of the Spinal Column

In this post I’d like to provide a review of the common pain generators in and around the spine relating to traumatic injuries. Obviously this is not an exhaustive list and focuses on traumatic etiology; it also does not include physical examination tests or medication treatment options. Nonetheless, the vast majority of cases involving pain at or near the spine following injury or trauma are due to pain from one or more of the following sources.

Pain generator is a term commonly used in healthcare settings including education, research, and clinical practice to identify, as concisely as possible, the singular body part or “tissue” which is causing a pain. This source could be described as a particular piece of anatomy (e.g. intervertebral disc) or a specific condition relating to a particular piece of anatomy (e.g. intervertebral disc herniation). It should be noted that identifying the pain generating tissue does not imply any specific etiology or reason for why it is hurting (e.g. facet joint pain can be traumatic or arthritic). Physical examination, thorough interviewing, and good documentation are therefore critical in order to link a pain generator with a mechanism of injury or traumatic etiology.

The Jelly Donut: Each disc has a gelatinous inner nucleus pulposus, the “jelly”, contained within a solid annulus. The annular fibers are flexible but have a shape they should return to, like an ear. Herniation of the pulposus through the annulus compromises the hydrostatic/hydraulic pressure in the disc which greatly compromises its stability.

Intervertebral discs (IVD) are probably the most referenced, researched, and talked-about spinal pain generator resulting from motor vehicle collisions. Injuries to discs like herniations are also common results of a slip-and-fall type injury if there is axial loading of the spine (vertically-oriented force “compressing” the spinal column). Magnetic Resonance Imaging (MRI) has made evaluation of IVDs readily available and permanent injury to the disc is often very apparent on MR studies as the shape of the disc changes on a large-enough scale to appreciate. These large-scale changes occur with significant restructuring of the disc on a microscopic scale, and these micro- and macro-scale structural changes: are permanent in nature, worsen over time, and contribute to accelerated degeneration of that disc over time.
Testing disc pain:  MRI can visualize discs, however research has shown that discs can appear to have a herniation with no reported pain; abnormal disc findings on MRI (e.g. disc herniation) should be correlated with a patient’s history of trauma and examination findings and clearly documented to establish a direct link between findings and symptoms
Treating disc pain:  Spinal mobilization/manipulation, physical therapy, traction therapy, laser therapy, flexion-distraction therapy, epidural steroid injections (ESI), intradiscal electrothermal therapy (IDET), surgery (microdiscectomy, disc replacement, fusion)


Facet joints, may be the field goal kicker of spinal pain generators. No one usually gives them much thought until they become vitally important for the situation at hand. But just as the kicker plays a major role in almost every game, whether it’s the game-winning play or not, the facets are “the joints” in the spine that get injured following trauma. While discs are very unique structures anatomically, facet joints are very similar to most other joints in the body. As such, they are susceptible to a sprain injury from trauma if they are violently impacted (e.g. neck whips backwards) or violently stretched (e.g. neck whips forwards). With 24 bones in the spinal column and a left and right facet joint conjoining each, I often say “That’s 48 opportunities for a ‘rolled-ankle’ type injury in your spine; 14 in the neck alone!”
Testing facet pain:  Movement-based imaging (diagnostic motion x-ray or static x-ray in flexion and extension positions) can show abnormal gapping of joints or slipping of bones which would indicate facet joint instability, MRI may show facet joint effusion, anti-inflammatory facet joint injections are both a diagnostic and treatment option in one procedure, medial bundle branch blocks (MBBB) use a numbing agent to the pain-sensitive nerves of the facet joint for diagnostic purposes only (temporary pain relief indicates facetogenic pain)
Treating facet pain:  Spinal mobilization/manipulation, traction therapy, laser therapy, flexion-distraction therapy, rehabilitative exercises for stabilization, facet joint injections, surgery, neurotomy/nerve ablation (e.g. RFA)

Discs are innervated from the outside in and the extent/depth of innervation varies between individuals. This picture also demonstrates innervation of the anterior longitudinal ligament in front of the disc (star) and the posterior longitudinal ligament (PLL) behind the disc (arrow). The PLL is strongly attached to the discs and contains nociceptive nerve fibers (nerves that transmit pain) along with the outer portion of the disc itself.

Nerves are everywhere, and since all pain is transmitted by nerves you could almost say “All pain is nerve pain” (e.g. RFA to eradicate a nerve is treating pain from a facet joint). But here I’m talking about spinal nerves as a pain generator. Nerves exit the spinal canal through little holes between each pair of vertebrae at which point we call them spinal nerves or spinal nerve roots. This is where nerves are often compressed by a herniated disc or facet joint arthritis, and these same things can also cause a narrowing of the central spinal canal which can also result in pain among other symptoms (this is called stenosis). After leaving the spinal area, nerves can also be compressed as they course through the body in tunnels or between tight muscles. In addition to pain, injured nerves can also produce symptoms of tingling, numbness, and weakness.
Testing nerve pain:  MRI to visualize nerves and if/how they are physically compressed, Nerve Conduction Velocity (NCV) to assess nerve function as opposed to structure although this is best suited for nerves outside the spine or radicular nerve symptoms in the arms or legs. Nerve blocks can determine if a nerve is sending the pain signal in question although it may simply be the messenger (as in MBBB above)
Treating nerve pain:  Spinal mobilization/manipulation, traction therapy, or laser therapy can be effective for spinal nerves not under constant compression. Structurally-compressed spinal nerve roots typically require surgical correction. Soft tissue therapy (manual therapy, myofascial release, stretching) can be beneficial for nerves compressed by excessively tight muscles. Nerve blocks can provide excellent nerve pain relief although it is usually short-lived.

Muscles are typically a major contributing factor to the high pain level around the spine following trauma, but most muscles around the spine are not prone to intrinsic permanent damage.  Tendons, which attach the contracting part of the muscle to bone, are permanently damaged when they are ruptured or torn (partially or fully), but spinal muscles’ tendons are not prone to tears in this sense. Muscle spasms and pain are common side effects of permanent injuries to the discs or facet joints, however, and so management of muscular pain becomes a part of managing the chronic aspect of these injuries as a whole. Various therapies and myofascial trigger point injections are treatment options.

It is paramount for medicolegal cases (auto accidents) that your physician is able to understand and support a finding or diagnosis from a test like an MRI as correlating (or not correlating) to your mechanism of injury, subjective complaints, and examination findings in documentation that stands firmly against the rigors of the court.