The muscles of the lower back help stabilize, rotate, flex, and extend the spinal column, which is a bony tower of 24 vertebrae that gives the body structure and houses the spinal cord. The spinal cord and its nerves are the means by which the body and brain communicate with one another. Together, the brain and spinal cord make up the central nervous system.

The spine’s four sections, from top to bottom, are the cervical (neck), thoracic (abdomen,) lumbar (lower back), and sacral (toward tailbone). Throughout the spine, intervertebral discs made of cushioning material both pad and connect the vertebrae.

The lumbo-sacral spine includes:

  • Lumbar vertebrae: Numbered L1 through L5, these odd-shaped vertebrae signal the end of the typical bones of the spinal column.
  • Sacrum: This triangle-shaped bone is made up of five fused vertebrae. It fits like a wedge into the back of the pelvis at the hips.
  • Coccyx: This small bone is better known as the tailbone.

Muscles connect to the vertebrae and bones via ligaments, flexible bands of fibrous tissue. The deep muscles of the back fit into or affix parts of themselves to the grooves in the spinous processes, or the protrusion of the bone than can be felt through the skin.

Important muscles of the lumbar spine include:

  • Multifidus: This long muscle travels nearly the entire length of the back. It stabilizes and rotates the lumbar spine.
  • Longissimus: Another long muscle, this one begins in the middle of the lumbar spine and continues up to the transverse process.
  • Spinalis: This superficial muscle begins as a thick tendon from the sacrum and travels up into the neck, inserting at the spinous processes of the cervical vertebrae.

Lower back pain is a common ailment. This can arise for reasons ranging from improper posture to a compression fracture. Lower back issues can put pressure on the lumbar spine nerves and create even stronger pain as the nerves become pinched or irritated from friction. Some common causes of reoccurring lower back pain include:

  • Muscle injury, which can occur from overuse or a sudden injury
  • Fractured vertebrae
  • Herniated disc, or damage to the cushioning between vertebrae
  • Spinal stenosis, or narrowing of the spinal canal
  • Osteoarthritis, a degenerative bone disease