Causes of Acute Low Back Pain

What is acute low back pain?
The most common condition that the physiatrists of Long Island Spine Rehabilitation are called upon to evaluate and treat is acute low back, or lumbar, pain. Acute low back pain (LBP) can be defined as low back pain which persists for up to six weeks. It may be described by patients as an aching, burning, or stabbing sensation, and the quality of the pain can be sharp, dull, well-localized, or more diffuse in location. The intensity of pain may range from mild to severe and may fluctuate. The symptoms from this typically benign condition can be quite debilitating with exacerbations resulting from fairly trivial maneuvers such as a simple bend, light lift, a cough, or sneeze. The pain may radiate into one or both buttocks or even into the hip or thigh area. Low back pain may also begin following a more strenuous activity or acute trauma but often is seemingly unrelated to a specific activity. Acute LBP is often thought of as the result of repetitive overuse rather than pain arising from a singular event. The pain may begin suddenly or develop more gradually over a period of weeks.

Who experiences acute low back pain?
At least 80% of individuals experience a significant episode of LBP at some point in their lives. At any given point in time, approximately 15% of individuals report that they are experiencing at least mild LBP. Some consider the symptom of LBP to be an anticipated part of the human experience. Acute LBP events remind us that despite the brilliance of our spinal design, we do come with design flaws, and these include the potent of ability of the spinal structures to generate pain. Injury to these pain generators results from more stressful events but most commonly from repetitive daily wear and tear.

What causes low back pain?
Patients presenting to our office are typically understandably concerned about the severity and origin of their pain. At Long Island Spine Rehabilitation Medicine, a good deal of time is spent educating our patients. Education and information is of particular importance in instances of debilitating and acute LBP, as patients with this condition are often frightened by the intensity of their symptoms. The exact source of acute LBP is often difficult to identify. In fact, there are numerous possible spinal pain generators including muscles, soft connective tissue, ligaments, joint capsules and cartilage, and even blood vessels. These anatomic structures of the spine may be pulled, strained, stretched, sprained or bruised. Additionally, and perhaps more commonly than previously theorized, annular tears (small tears that occur in the outer layer of the intervertebral disc) can initiate severe pain. Even if the actual tissue damage is minor, and likely to repair quickly, the pain experienced may be quite severe. It is important to understand that these spinal anatomic components (i.e. the intervertebral disc, facet joints, and the sacroiliac joint) have a nerve supply of their own. Therefore, when such structures are injured, similar to a tear in a meniscus of the knee, pain can result. As the nerve supply to these structures is often very rich, the resultant pain can be severe. Once the pain generating abilities of these structures is explained, it becomes clearer to patients how spinal pain can result without a “sciatica” or nerve root / radicular origin. The latter syndromes arise from a spinal nerve being compressed and inflamed by a disc herniation or spinal stenosis.

No matter which tissue is initially irritated, a cascade of events occurs which contributes to the acute LBP experience. Numerous chemical substances are released in response to tissue irritation and injury. These substances “stimulate” the surrounding pain sensitive nerve fibers, resulting in the sensation of pain. Some of these chemicals trigger the process of inflammation, or swelling, which also contributes to pain. The chemicals associated with this inflammatory process feed back more signals which perpetuate the process of swelling. The inflammation attributable to this cycle of events may persist for days to weeks. Muscular tension (spasm) in the surrounding tissues may occur. While patients will often refer to their pain as a primary muscle spasm, the muscular component and spasm are often believed to be secondary to stimulation by a deeper seated and more potent pain generator. Studies have actually demonstrated that the deeper anatomical structures of the spine, such as the discs and facet joints, are more likely to cause debilitating lumbar pain events than the more superficial muscle and ligamentous tissues. At times the muscle spasm, or reflex contraction, component can be so pronounced that a “trunk shift” (the body tilts to one side more than the other) results. Finally, a relative inhibition or lack of the usual blood supply to the affected area may occur so that nutrients and oxygen are not optimally delivered and removal of irritating byproducts of inflammation is impaired.

The good news is that even if the exact source of pain is not determined and the pain is severe, usually the acute pain subsides spontaneously over time. The physiatrists of Long Island Spine Rehabilitation Medicine will take a detailed history and perform a comprehensive examination to make certain that your pain is of a more benign and musculoskeletal origin and not related to a more concerning medical condition. In some instances, there may be a role for imaging of the lumbar spine. Initial imaging modalities can include X-ray or plain radiographs, with advanced imaging approaches such as MRI and CT scans reserved for more concerning or persistent cases of LBP. Fifty percent of acute LBP episodes nearly completely resolve within two weeks, and 80% by six weeks. Unfortunately, the duration and severity of a single episode cannot be predicted based on the onset, location of pain, or even the initial severity of symptoms. Excruciating initial pain may resolve within several days, while moderate or mild symptoms may persist for weeks. A smaller percentage of individuals will experience recurrent pain or develop persistent pain in the future.

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