The Functions of the Lumbar Spine

The low back is the part of the spinal column that consists of the lumbar spine, the sacrum and the coccyx.

In a normal, healthy spine, the lumbar vertebrae stack on top of one another in a centered alignment.

While all vertebrae have approximately the same shape, the lumbar bones are the largest. This is because they carry a (larger) load transmitted from the top of the head down to the low spine.

Another reason why the lumbar bones are larger than the cervical and thoracic vertebrae is that they must be big and strong to support the muscles and bones during movement. The lumbar area of the spine is the physical center of the body. This area is the hub for many basic activities, including balance and the generation of locomotion (walking and running, etc.) The demands on the lumbar area are great.

The front of the lumbar vertebra is like a thick round disk. Above and below each vertebra is an intervertebral disk.

The lumbar vertebrae take the load coming down the spine, thereby supporting the body's weight.

The back of the vertebra is more complicated, with protrusions and valleys, each with a purpose integral to the spine. The bone extends out from the back of the vertebra to form canals for nerves, joints for stability, and attachment sites for muscles. Here is a list:

• Spinous process
• Transverse process
• Facet joint
• Lamina
• Pedicle
• Pars interarticularis

Each region of the spine has a directional curve associated with it. The normal curve of the lumbar spine is a lordosis.

The lumbar spine rests upon the sacrum. The place where they meet is called the lumbosacral joint, or L5-S1.

The L5-S1 junction is where the injury spondylolisthesis occurs.

The sacrum is a flat triangular bone located below the lumbar spine. It functions as a wedge between the 2 hip bones on either side of it, stabilizing the entire pelvic area. Many nerves exit out holes on each side of the sacrum, including the sciatic nerve, which is the source of pain for sufferers of sciatica.

The spinal curve reverses at the sacrum. The sacral curve is a kyphosis.

Below the sacrum is the coccyx bone.