Anatomy of the Lumbar Spine
In between each of the five lumbar vertebrae (bones) is a disc, a tough fibrous shock-absorbing pad. The disc is a combination of strong connective tissues, which hold one vertebra to the next, and acts as a cushion between the vertebrae. The disc is made of a tough outer layer called the “annulus fibrosus” and a gel-like center called the “nucleus pulposus.” As you get older, the center of the disc may start to lose water content, making the disc less elastic and effective as a cushion. Nerve roots exit the spinal canal through small passageways between the vertebrae and discs. Pain and other symptoms can develop when the damaged disc pushes into the spinal canal or nerve roots.
Differential Diagnosis – Degeneration vs Prolapse vs Herniation vs Nerve Compression
Disc Degeneration refers to a syndrome in which a painful disc can cause associated low back pain. The condition generally starts with an injury to the disc space. The injury weakens the disc and creates excessive movement because the disc can no longer hold the vertebrae above and below the disc together as well as it used to. This movement and inflammatory response irritate the area, commonly producing symptoms of low back pain (Stage 1 of picture). Unlike the muscles in the back, the lumbar disc does not have a blood supply and therefore cannot heal itself and degenerative disc disease can become chronic and lead to further problems.
*NB – Disc degeneration is part of the natural process of aging and does not necessarily lead to low back pain. MRI scans have documented that approximately 30% of 30 year olds have signs of disc degeneration on MRI scans even though they have no back pain symptoms. It must therefore be stressed that not all degenerated discs cause pain.
Herniated discs are often referred to as “slipped discs”, “bulging discs”, or “prolapsed discs”. This term is from the action of the nucleus tissue when it is forced from the center of the disc. The disc itself does not slip. However, the nucleus (soft inner layer) tissues located in the center of the disc can be placed under so much pressure that it can cause the annulus (outer tough layer) to rupture. This can be seen in its varying degrees of severity in the adjacent picture from stages 2-4. If severe, disc herniaiton may cause compression which can cause local and referred pain, numbness, or weakness in the low back. leg or foot. Approximately 90% of disc herniations will occur at L4- L5 (lumbar segments 4 and 5) or L5- S1 (lumbar segment 5 and sacral segment1), which causes pain in the L5 nerve or S1 nerve, respectively.
The sciatic nerve is the large nerve that extends down the spinal column to its exit point in the pelvis and carries nerve fibers to the leg. Sciatica is a condition in which a herniated or ruptured disc presses on the sciatic nerve. This compression causes shock-like or burning low back pain, with pain through the buttocks and down one leg to below the knee, occasionally reaching the foot. In extreme cases, when the nerve is pinched between the disc and an adjacent bone, not pain but numbness and some loss of movement control in the leg due may occur. The condition may also be caused by a tumor, cyst, or degeneration of the sciatic nerve root.
Signs and Symptoms
What Increases Your Risk?
Factors You Cannot Change
- Advancing age
- Males greater than females
- History of previous back injury
Factors You Can Change
- Your job or other activities such as long periods of sitting, lifting or pulling heavy objects, frequent bending or twisting of the back, heavy physical exertion, repetitive motions, or exposure to constant vibration (such as driving)
- Not exercising regularly, doing strenuous exercise for a long time, or starting to exercise too strenuously after a long period of inactivity
- Smoking – can impair spinal discs’ ability to absorb nutrients they need from the blood, making the discs more prone to injury.
- Being overweight – Carrying extra body weight (especially in the stomach area) causes additional strain on the lower back.
- Frequent coughing
In most cases, if a patient’s low back and/or leg pain is going to resolve after a lumbar herniated disc it will do so within about six weeks. During this time several conservative treatment options can help reduce the back pain, leg pain and discomfort caused by the herniated disc.
Physiotherapy treatment may include ultrasound, electric stimulation, hot packs, cold packs, traction of your lumbar joints, and manual “hands on” mobilisations to reduce your pain and muscle spasm. Manipulation may provide short-term relief from non-specific low back pain, but should be avoided in most cases of herniated disc to avoid further injury and/or compression. Non Steroidal Anti-inflammatory Medications (NSAIDS) e.g. nurofen may be helpful in alleviating the inflammation associated with low back pain, and stronger therapies, such as oral steroids or epidurals, may be prescribed to treat severe flares.
At first, your physiotherapist may prescribe gentle stretches or posture changes to reduce the back symptoms. When you have less pain, more vigorous exercises will be used to improve low back flexibility and strength, core stability, endurance and enable a safe return to full activity. In severe cases where disc degeneration and/or nerve compression does not respond to conservative treatments, surgery may be required.