Degenerative disc disease (DDD) is a common cause of sciatica. DDD describes the natural wear and tear that occurs in the spinal discs as a person ages. Sciatica is not a diagnosis itself but a symptom: a pain that radiates from the lower back, through the hips and buttocks, and down one leg. This radiating pain is caused by the compression or irritation of the sciatic nerve, which is the body’s longest nerve, formed by nerve roots emerging from the lower spine.
Understanding Degenerative Disc Disease
The spine relies on intervertebral discs to act as shock absorbers and permit flexibility between the vertebrae. Each disc is composed of a tough, fibrous outer ring called the annulus fibrosus, which encases a soft, gel-like center known as the nucleus pulposus. This composition allows the discs to handle the compressive forces placed on the spine during daily activities.
The degenerative process begins with the gradual loss of water content within the nucleus pulposus, often described as disc dehydration. As the disc loses fluid, it loses height and elasticity, diminishing its ability to absorb shock effectively. This reduction in disc height narrows the space between the vertebrae, which can destabilize the spinal segment.
The outer ring of the disc, the annulus fibrosus, also weakens and may develop tiny cracks or tears as a result of this increased stress. The term DDD describes these age-related structural changes that can lead to pain and instability. These changes in the disc structure set the stage for nerve irritation, which is the direct cause of sciatica symptoms.
The Mechanism of Nerve Root Irritation
The structural changes resulting from degenerative disc disease directly reduce the space available for the sciatic nerve roots to exit the spinal column. The sciatic nerve is formed by the nerve roots of the lower lumbar and sacral spine. When the discs in the lower back degenerate, they can cause sciatica through three main mechanisms that compromise these nerve roots.
One primary mechanism is the loss of disc height, which causes the space where the nerve roots exit the spine, known as the neural foramen, to narrow. This condition is called foraminal stenosis, and the reduced space mechanically pinches the nerve root. The chronic instability also stimulates the body to produce bony growths, called osteophytes or bone spurs, as a compensatory measure.
These bone spurs can form around the facet joints and disc margins, further encroaching upon the neural foramen and the central spinal canal, leading to nerve root compression. A third, often acute, mechanism is a disc herniation, which occurs when the weakened annulus fibrosus tears and the inner nucleus pulposus material pushes outward. This extruded material can press directly against the adjacent nerve root, causing inflammation and mechanical irritation.
The herniated disc material itself can also chemically irritate the nerve root due to the release of inflammatory substances. Sciatica from DDD is often a combination of mechanical compression and chemical irritation of the nerve roots.
Confirming Degenerative Disc Disease as the Cause
A medical professional’s first step in diagnosing DDD-related sciatica is a thorough physical examination and medical history review. The physical exam often includes specific tests, such as the straight leg raise test, which can reproduce the radiating leg pain and suggest nerve root irritation in the lumbar spine. The doctor will also check for muscle weakness, changes in reflexes, or altered sensation patterns that follow the distribution of a specific nerve root.
To confirm the structural basis of the symptoms, imaging studies are typically ordered to visualize the spine. X-rays are useful for showing the loss of disc height and the presence of osteophytes, which are clear signs of degeneration and bony encroachment. A Magnetic Resonance Imaging (MRI) scan provides a more detailed picture, allowing doctors to visualize the soft tissues.
The MRI can show the degree of disc dehydration, any active disc herniation, and the extent of nerve root compression or inflammation. Correlating the imaging evidence of disc degeneration and nerve compression with the patient’s exact pattern of radiating pain is necessary to definitively link the sciatica to the underlying degenerative disc disease.
Treatment Options for DDD-Related Sciatica
The initial approach to managing sciatica caused by degenerative disc disease is generally conservative, focusing on reducing nerve inflammation and restoring spinal function. Physical therapy is a primary conservative treatment, emphasizing core strengthening exercises to stabilize the spine and reduce mechanical stress on the discs and nerve roots. Specific stretching and movement patterns are employed to improve spinal mobility and reduce pressure on the irritated nerve.
Medication options include over-the-counter non-steroidal anti-inflammatory drugs (NSAIDs) to reduce inflammation, or prescription muscle relaxants for associated muscle spasms. For more intense pain and inflammation, targeted epidural steroid injections may be administered. These injections deliver anti-inflammatory medication directly into the epidural space near the compressed nerve root, providing significant relief.
When conservative treatments fail to provide adequate relief, or if there is progressive neurological deficit, surgical options may be considered. A microdiscectomy is a procedure used to remove the portion of a herniated disc that is pressing on the nerve root. For cases involving severe foraminal stenosis or spinal instability, procedures like a lumbar laminectomy or spinal fusion may be performed to widen the spinal canal and stabilize the vertebral segment.