Lumbar Spine

The lumbar spine is the lower back that begins below the last thoracic vertebra (T12) and ends at the top of the sacral spine, or sacrum (S1). Most people have 5 lumbar levels (L1-L5), although it is not unusual to have 6. Each lumbar spinal level is numbered from top to bottom—L1 through L5, or L6.

The low back vertebral bodies are larger, thicker block-like structures of dense bone. From the front (or anterior), the vertebral body appears rounded. However, the posterior bony structure is different—lamina, pedicles and bony processes project off the back of the vertebral body. These processes and vertebral arches create the hollow spinal canal for lumbar nerves structures and the cauda equina.

lumbar spinal columnDetailed views of the lumbar spinal column and bony anatomy. Photo Source: Shutterstock.com.

The lamina, a thin bony plate shields or protects access to the spinal canal. Some people who have lumbar spinal stenosis may undergo a surgical procedure called decompressive laminotomy or laminectomy. The procedure involves removing part of all of the lamina at the affected level and enlarging the space around the compressed nerves.

Lumbar Structures Create Strong Joint Complex

A single intervertebral disc separates 2 vertebral bodies, and together with the facet joints forms a strong joint complex that enables the spine to bend and twist. One pair of facet joints from the top (or superior) vertebral body connects to the lower (or inferior) pair of facet joints. The facet joints are true synovial joints meaning they are lined with cartilage and the joint’s capsule encases synovial fluid that enables joints to glide during movement.

  • Facet joint syndrome may develop as a consequence of aging and degenerative spinal changes and cause lower back pain.

Lumbar intervertebral discs are secured in place by the fibrous endplates of the superior and inferior vertebral bodies. The gel-like center of each disc, called the nucleus pulposus is encased or surrounded by the annulus fibrosus—a tough layer of fibrocartilage that could be likened to a radial tire.

Discs are integral to the joint complex and function to (1) hold the superior and inferior vertebrae together, (2) bear weight, (3) absorb and distribute shock and forces during movement, and (4) create open nerve passageways called foramen or neuroforamen. The neuroforaminal spaces at either side of the disc level allow nerve rootlets to exit the spinal canal and leave the vertebral column.

  • Lumbar disc herniation is a common cause of lower back pain that can radiate into one or both legs, called lumbar radiculopathy. This condition can develop when lumbar nerves are compressed.

Low Back Supported by Lumbar Ligaments, Tendons and Muscles

Systems of strong fibrous bands of ligaments hold the vertebrae and discs together and stabilize the spine by helping to prevent excessive movements. The 3 major spinal ligaments are the (1) anterior longitudinal ligament, (2) posterior longitudinal ligament and (3) ligamentum flavum. Spinal tendons attach muscles to the vertebrae and together work to limit excessive movement.

lumbar ligamentsLumbar spinal ligaments support the low back and help limit excessive movement. Photo Source: Shutterstock.com.

Lumbar Spine Nerves

The spinal cord ends between the first and second lumbar vertebrae (L1-L2). Below this level, the remaining nerves form the cauda equina, a bundle of nerves resembling a horse’s tail. These small nerves transmit messages between the brain and structures in the lower body, including the large intestine, bladder, abdominal muscles, perineum, legs and feet.

4 Ways to Protect Your Low Back

Considering upwards of 80% of adults will visit a doctor for lower back pain at some point in their life, it pays to take care of your lumbar spine to help avoid painful, unnecessary wear-and-tear to this vulnerable segment of your spinal column. You can minimize your risk of a lower back problem by:

1. Lose weight. Even a 10-pound loss can help reduce lower back pain.

2. Strengthen and maintain core (abdominal) muscles. The abdominal and lower back muscles work together to form a supportive “girdle” around your waist and lower back. Stronger muscles can help stabilize the lower back and can help reduce injury risk.

3. Stop smoking. Nicotine reduces blood flow to the spinal structures, including the lumbar discs, and can accelerate age-related degenerative changes.

4. Proper posture and body mechanics. Keep your spine erect and lift objects with your legs. Always ask for help to carry heavy objects. Although your lumbar spine is capable of bending and twisting simultaneously, you should avoid doing so.

Updated on: 03/13/20
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Facet Joints of the Spine's Anatomy
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Facet Joints of the Spine's Anatomy

A joint is where 2 or more bones are joined. Joints allow motion (articulation). The joints in the spine are commonly called facet joints, and you can learn about the anatomy of spinal joints in this article.
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