The lumbar vertebrae consist of five individual bones that form the spine in the lower back. The complex anatomy of the lumbar spine is a remarkable combination of these strong vertebrae, as well as multiple bony elements linked by joint capsules, flexible ligaments, large muscles, and highly sensitive nerves. The lumbar spine is designed to be incredibly strong, protecting the highly sensitive spinal cord and spinal nerve roots. At the same time, it is highly flexible, providing for mobility in many different planes including flexion, extension, and to a lesser degree, side bending and rotation.
The lumbar vertebrae are stacked to form a continuous column in order from superior (L1 or first lumbar vertebra) to inferior (L5 or fifth lumbar vertebra). Together they create the concave lumbar curvature in the lower back. Connecting each vertebra to its neighbouring vertebra is an intervertebral disc made of tough fibrocartilage with a jelly-like centre. The outer layer of the intervertebral disc, the annulus fibrosus, holds the vertebrae together and provides strength and flexibility to the back during movement. The jelly-like nucleus pulposus acts as a shock absorber to resist the strain and pressure exerted on the lower back.
The lumbar vertebrae are some of the largest and heaviest vertebrae in the spine, second in size only to the sacrum. A cylinder of bone known as the vertebral body makes up the majority of the lumbar vertebrae’s mass and bears most of the body’s weight. The vertebral foramen is a large, triangular opening in the center of the vertebra that provides space for the spinal cord as it passes through the lower back.
Several bony processes extend from each vertebrae and are involved in muscle attachment and movement of the lower back. The spinous process extends from the posterior end of the arch as a thin rectangle of bone. It serves as a connection point for the muscles of the back and pelvis, such as the hip flexors and spinal erectors. On the left and right sides of each vertebra are the short, triangular transverse processes. The transverse processes form important connection points for many muscles, including the muscles that extend and rotate the trunk.
The lumbar spine is an intricate system and injury to the vertebrae, joints, discs, muscles, ligaments, and nerves can all be a source of pain. Posture, core strength, spinal mobility, and flexibility are all important factors that should be addressed if you have low back pain or are looking at ways to prevent further recurrence of low back pain.
