Low back pain is often poorly understood, not only by the patient but also by health care providers. The reason for this uncertainty lies in the causes of low back pain. Low back pain has been labeled as a “waste basket” diagnosis. Similar to a waste basket, where items from multiple sources can be found, pain in the low back may occur as a result of irritation or injury to a number of tissues.
The intervertebral disc is most commonly implicated as a cause of low back pain. However, many other tissues have been demonstrated to contribute to low back pain. These include muscles, ligaments, nerve roots, bones, joints and even skin and fascia. So, when faced with low back pain, how does one tackle the challenge?
The most important question to answer when faced with low back pain is whether or not the low back pain is associated with radiating pain to the lower extremities. Radiating pain to the extremities is often referred to as radicular pain or radiculopathy. This includes pain that may be described as shooting below the knee and is often referred to as sciatica or pain radiating along the sciatic nerve distribution. Not all radicular pain to the lower extremities is sciatica, as pain that radiates along the front of the thigh may be due to irritation of a nerve root that is not part of the sciatic nerve.
When patients are experiencing radicular pain or sciatica in addition to the low back pain, then it is likely that there is a cause for nerve irritation and that may be frequently addressed ahead of other causes of the low back pain that may co-exist. Nerve irritation occurs most often at the site where nerves exit the spinal canal. There, they are referred to as nerve roots.
The nerve roots are prone to irritation because they exit the spine through small openings. Any structure that narrows that space, such as a herniated disc or spinal stenosis can result in radicular symptoms and usually also, low back pain. There is one exception: low back pain that may be associated with pain referred along the back of the thigh. In this case, the patient may be treated as though he/she suffers only from low back pain.
A muscle deep in the buttock, known as the piriformis runs right on top of the sciatic nerve and may cause low back, buttock and/or lower extremity pain. This is referred to as the piriformis syndrome.
Pain present only in the low back, is often referred to as axial low back pain. In younger people, axial low back pain may be “discogenic”. Discogenic low back pain or discogenic pain is due to degeneration of the disc and is sometimes referred to as degenerative disc disease.
As we age, the discs undergo a degenerative process whereby there is leakage of the contents of the inner, more hydrated, part of the disc. This happens as a result of the formation of small fissures that allow the leakage of the contents of the inner part of the disc to the surrounding tissues which include nerve fibers. The chemicals that leak are irritating to nerves and cause pain. Pain is worse in positions that increase the internal pressure of the disc, such as prolonged sitting, bending and lifting.
Other causes of axial low back pain may originate in the joints. These include the facet joints or the sacroiliac joint or simply SI joint. Pain originating from these joints may occur more with maneuvers that involve position changes such as twisting motion for the facet pain and hip motion the SI joint pain. As with other joint problems, degeneration and aging can increase the likelihood of pain.
Treatment of low back pain differs based on the etiology. The ultimate goal of any therapy is always functional rehabilitation, i.e. going back to doing whatever one was able to do prior to the onset of pain. Interventions used in the management of low back pain include diagnostic blocks and therapeutic interventions. Examples of diagnostic blocks used in the treatment of low back pain include diagnostic discography (or discogram) and diagnostic facet nerve blocks. Examples of therapeutic interventions in the management of low back pain and radiculopathy include epidural steroid injections, facet nerve radiofrequency ablation and IDET. Other injections may be both diagnostic and therapeutic such as sacroiliac joint injections. Physical therapy is often prescribed with therapeutic procedures and medications are prescribed as needed to assist in the rehabilitation process.