Lower back pain explained – Pathologies of the lumbar spine

Back pain, in particular lower back pain is a condition which affects many people every day. However, the term lower back pain is very general and does not specify the underlying cause of pain or pathology. Lower back pain generally refers to pathologies of the lumbar spine but is also often used to describe pathologies of the pelvis and sacro-illiac-joint. For the purpose of this article we will be focussing on the main pathologies of the lumbar spine.

The lumbar spine is made up of the five largest vertebrae in the spine, each separated by intervertebral discs, which are subjected to the greatest compressive loads in the spine. The orientation of the facet joints in the lumbar spine allow for mainly flexion and extension based movements with a limited amount of rotation, particularly the lower lumbar vertebrae.

Lumbar Disc Bulge

The most common pathology of the lumbar spine is lumbar disc bulge. This refers to a tear in the annulus fibrosis (outer fibrous layer of intervertebral disc) allowing the nucleus pulposus (inner liquid portion of the disc) to bulge, most commonly posteriorly and anteriorly in very rare cases.

This disc bulging can cause compression of the nerve roots, resulting in radiating pain and distal weakness of the corresponding areas of the body which those nerves innervate. People with posterior lumbar spine disc bulges will typically present with pain on flexion based (forward bending) movements of the lumbar spine. They will generally find extension based (backward bending) movements relieving.

In the rare case of anterior disc bulge, people will present with the opposite pattern. However imaging such as MRI is often required to confirm this. Risk of lumbar disc bulge is often associated with increasing age, participation in activities which involve repeated flexion and rotation movements and heavy lifting.

Lumbar Facet Joint Irritation

Lumbar facet joint irritation is the other main pathology of the lumbar spine. The facet joints are the posterior synovial joints between vertebrae and can be irritated or damaged by activities which put too much load on them. This includes activities that involve repeated lumbar extension and rotation such as fast bowling in cricket.

People with lumbar facet joint irritation will generally present with stiffness and discomfort with extension based movements of the lumbar spine and flexion based movements and stretches will often relieve pain to some degree. Activities such as prolonged standing or lying down on the back will often reproduce pain with lumbar facet joint irritation.

Other Causes of Back Pain

Two of the other main pathologies of the lumbar spine include spondylolisthesis and spinal canal stenosis. Spondylolisthesis refers to the forward slipping of one lumbar vertebra on the segment below, often as a result of repetitive extension based activities. This condition will often present similarly to facet joint irritation when symptomatic, however a step deformity (due to the forward slippage of the effected segment) will often be felt, with significant instability at that segment.

Spinal canal stenosis refers to the narrowing of the spinal canal which may cause compression of the spinal cord and exiting nerve roots. This often occurs with increasing age as a result of degeneration; however it can also be caused from disc bulge, osteophyte formation, spondylolysthesis or calcification of the intervertebral ligaments.

People with lumbar spinal canal stenosis will often present with pain when walking (claudication), weakness and a loss of deep tendon reflexes.

In any case, thorough assessment of the lumbar spine is required to determine the underlying pathology which is causing lower back pain. Thorough and accurate assessment and diagnosis of lower back pain will allow for more specific treatment, resulting in greater clinical outcomes.

By Jack Hickey

Exercise Physiologist at MD Health Pilates

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