The muscles of the lower back help stabilize, rotate, flex, and extend the spinal column, 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. Together, the brain and spinal cord make up the central nervous system.

The multifidus is a long muscle that travels nearly the entire length of the back. It stabilizes and rotates the lumbar spine. One important feature is how it takes the pressure off vertebral discs, padding between vertebrae, so the body’s weight can be evenly distributed.

The multifidus starts at the base of the spin at the sacrum and extends up the second vertebrae in the neck. The muscle features multiple insertion points along the spine, specifically into the spinous process of each vertebra. 

It can be felt through the skin to the immediate left and right of the vertebrae.

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

Lower back pain is a common ailment and one study published in the European Spine Journal found that people with chronic back pain often have a smaller multifidus muscle than those without chronic back pain.