Low back pain generators—what causes low back pain and how to classify it

Classifying low back pain

Whenever we attempt to classify low back pain, it is important to remind ourselves that LBP is merely a symptom that points to an underlying disease.

Different types of LBP are prevalent amongst different age groups. For instance, the main causes in infancy and adolescence are infections and spondylolysis. Among young male adults, premature disc degeneration, disc herniation, spondyloarthropathies and trauma represent the most common causes of low back pain. In middle-aged and older patients, nine out of ten LBP cases are caused by disc degeneration and its consequences. In the older age groups, red flag LBPs become commoner causes include infections, osteoporotic compression fractures and tumors. this is in addition to causes found in middle aged groups.

The most widely used LBP classification system is the aetiologic classification, which organizes low back pain into five groups. Apart from spondylogenic aetiologies, there are also neurogenic, viscerogenic, vasculogenic, and psychogenic aetiologies.

Spondylogenic low back pains 

Spondylogenic LBPs are disorders of anatomic components of the spine such as bones, facet or sacroiliac joints, or soft tissues including the muscles, ligaments, or intervertebral discs. As a general principle, these spondylogenic pains are often aggravated by motion and, conversely, relieved by rest. However, this is not always the case. Spondylogenic LBPs include degenerative Lumbar spine diseases, inflammatory diseases, trauma, infection, tumors, metabolic diseases, and non-specific low back pain, and it is worth looking briefly at some of these conditions:

• Degenerative lumbar spine diseases, or rather degenerative disc conditions, are comparatively common. They are often age-related and can be aggravated by lifestyle, disease, infection, or trauma. The resulting discogenic pain is commonly made worse by sitting, bending, lifting, or straining. In relation to disc degeneration, discogenic pain will often precede facet osteoarthritis, as degenerative disc conditions are usually harbingers or precursors of facet degeneration. Facet degeneration is often associated with abnormalities of the rhythm of the movement at joints of the back. It may or may not be associated with radicular pain and symptoms and is often worsened by extension type activities. There presentation as well as the magnitude of pain is usually a factor of mechanical, psychosocial, and neuropathic contributors. Pain may be relieved partially with rest.

• Another LBP of spondylogenic aetiology is inflammatory spine pain. Among the causes are conditions such as spondyloarthropathies, ankylosing spondylitis, psoriatic and reactive arthritis, and enteropathic spondyloarthropathies. Patients are genetically predisposed to these conditions, and their onset is often insidious. Another typical feature of inflammatory LBPs is that they tend to be worse after periods of rest. Symptoms such as stiffness are often worse in the morning and will improve with activity. Similarly, the stiffness will come back after prolonged inactivity during the day. One of the major differences between inflammatory and degenerative spine pain is that the former often worsens with inactivity while the later gets better. Also, the former involves other non-spinal joints such as in the hips, shoulders, hands, and feet. Corresponding x-ray images are also usually different, showing squared vertebral bodies, the so-called bamboo spine, sacroiliac pseudo-widening erosion, sclerosis of the sacroiliac joint, and periostitis and spurs at the enthuses.

• Trauma as a cause of low back pain is characterized by varying onsets and varying degrees of severity. Minor injuries, which may only affect the soft tissues around the low back, can result in mild to moderate pain. Its onset is often delayed and may initially present as discomfort, with the pain getting worse over subsequent days and possibly resulting in intermittent pain, or at times it becomes a chronic pain condition. Major traumas, on the other hand, usually result in severe pain with an immediate onset severe pain which may also be associated with neurologic deficits.

• Practicing in a tropical climate, one regularly encounters infection as a cause of LBP. Pyogenic infections have replaced mycobacterial infections as the most common cause, as treatment options for the latter have much improved with the advent of good antibacterial drugs. Fungal infections can also lead to LBP. The pain is usually worse at night and during times of rest. Infection-induced LBP is often associated with night sweats as well as chills. There may have been a history of the infection in other parts of the body. In children, there is often a history of respiratory tract infection, while elderly patients often present with urinary tract infections. This is more common amongst immunocompromised patients, such as diabetics or HIV patients and Steroid users. Also susceptible are children, juveniles who engage in drug abuse, and elderly patients.

• Primary or secondary tumors can also cause spondylogenic LBP, pain is often constant and worst during periods of physical inactivity. Vertebral destruction and instability are associated with mechanical pain. Many tumor patients have associated constitutional symptoms such as weight loss, malaise, appetite loss, and at times even associated infections in other parts of the body. Primary tumors, such as lymphoma or haemangioma, and secondary tumors in the breast, lungs, thyroid, kidneys, prostate, and the larger intestines are common.

• Osteoporotic fractures are also among the possible causes of spondylogenic LBP. They are common in postmenopausal and elderly women but can also be seen in younger patients who indulge in steroid abuse. Also at a higher risk are younger women who have had certain gynecological surgeries. Osteoporotic fractures usually occur because of multiple subtle traumas but may also be caused by a single event. The associated LBP has an immediate onset, and there may also be associated neurological deficits. The pain is often constant and severe, and is aggravated by movement, physical activity, and weight bearing. Most patients will complain that their pain is worse in sitting positions because often, it will be an exhale type pain.

Non-spondylogenic low back pains

LBPs can also have underlying causes in parts of the body other than the spine. These are known as non-spondylogenic LBPs, and they can be classified into the following four categories:

• Neurogenic low back pains originate in the lumbar nerve roots, often because herniated or bulging discs cause irritation or tension. Compression, such as in spinal canal stenosis, can also be a cause. Subtle tumors including neurofibroma, neurilemmoma, ependymoma as well as cysts and other tumors involving the nerve roots can also lead to neurogenic LBP. In addition, arachnoid irritation from any cause as well as tumors of the spinal dura may also cause this type of low back pain.
  However, apart from the pain, there are usually also accompanying neurologic components such as numbness, or weakness. Some patients may also experience associated bisphincteric dysfunction. 

• Vasculogenic low back pains usually originate from large blood vessels around the spine in the retroperitoneal space. One common cause is an abdominal aortic aneurysm, another is peripheral vascular disease. An abdominal aneurysm typically presents with boring-type deep-seated lumbar pain that is not usually related to activity. 

• Superior gluteal artery insufficiency presents with buttock pain resembling claudication that is aggravated by walking and relieved by standing still. The pain may radiate to the leg much like sciatic pain does. Vascular pain can usually be differentiated by the fact that it is not precipitated by activities that puts stress on the spine such as bending, stooping, or lifting. 

• Viscerogenic low back pains do not originate in the spine but rather in the visceral structures in the retroperitoneal area. These include the kidneys, the lungs in the proximal lumbar spine area, the pleura, the pancreas, the gallbladder, and the rectum, the intrapelvic organs, and the pelvic viscera. 

• In female patients, the uterus, the fallopian tubes, and the ovaries; in males, the prostate may be the cause. When any of these organs are diseased, they may cause LBP. However, cases that do present with low back pain are often either tumorous, or there is some type of infection. It may be a sign that a patient requires urgent attention.

• Pure psychogenic low back pain is rare, but it can be a component of chronic low back pain in some patients. In other cases, psychological conditions can go along with low back pain, and it can create confusion in terms of arriving at a clear clinical picture. Thorough investigation and evaluation of the patient will often help in the analysis.

Broadly speaking, the question whether pain comes from the organs, or the spine can often be answered by looking at a patient's history and physical examination. Viscerogenic back pain is neither aggravated by activity, nor is it relieved by rest, so patients with severe viscerogenic pain will often writhe and move around in the hope of getting relief. Spondylogenic pain patients on the other hand tend to lie perfectly still. 


Continue reading to part 2 of this Guest Blog post on approaches to management of low back pain