Lumbar disk disease is caused by a change in the structure of the normal disk. Most of the time, disk disease happens as a result of aging and the normal break down that occurs within the disk. Sometimes, severe injury can cause a normal disk to herniate. Injury may also cause an already herniated disk to worsen.
The vertebral column, or backbone, is made up of 33 vertebrae that are separated by spongy disks. The spine is divided into 4 areas:
- Cervical spine: The first 7 vertebrae, located in the neck
- Thoracic spine: The next 12 vertebrae, located in the chest area
- Lumbar spine: The next 5 vertebrae, located in the lower back
- Sacral spine: The lowest 5 vertebrae, located below the waist, also includes the 4 vertebrae that make up the tailbone (coccyx)
The lumbar spine consists of 5 bony segments in the lower back area, which is where lumbar disk disease occurs.
- Bulging disk. With age, the intervertebral disk may lose fluid and become dried out. As this happens, the spongy disk (which is located between the bony parts of the spine and acts as a “shock absorber”) becomes compressed. This may lead to the breakdown of the tough outer ring. This lets the nucleus, or the inside of the ring, to bulge out. This is called a bulging disk.
- Ruptured or herniated disk. As the disk continues to break down, or with continued stress on the spine, the inner nucleus pulposus may actually rupture out from the annulus. This is a ruptured, or herniated, disk. The fragments of disc material can then press on the nerve roots located just behind the disk space. This can cause pain, weakness, numbness, or changes in sensation.
Most disk herniations happen in the lower lumbar spine, especially between the fourth and fifth lumbar vertebrae and between the fifth lumbar vertebra and the first sacral vertebra (the L4-5 and L5-S1 levels).