When compared to other vertebra, the lumbar vertebrae are particularly large and heavy. A horizontal section of the lumbar vertebral body is elliptical in shape except for the posterior cavity that accommodates the spinal cord. The bodies of the three vertebrae, L2-L4, are wedge-shaped in the lateral view, having a greater vertical height anteriorly than posteriorly. Attached posteriorly to the body is the vertebral arch, consisting of two pedicles and a lamina that unites these. The arch and the body together surround the large vertebral foramen. The short and heavy pedicles arise from the upper part of the body making the superior vertebral notch more shallow than the inferior. The transverse processes project somewhat posteriorly and upward as well as laterally. On the posterior surface of the base of each transverse process there is typically a small tubercle which is called the accessory process. On the posterior surfaces of the suprerior articular process are more marked enlargements which are called the mammillary processes.

On the vertebral arch are projections that serve for attachment of muscles or for articulation with other bones. The typical projections are the spinous process that projects posteriorly from the midline of the lamina and the suprior articular processes that project upward on each side from the upper border of the lamina to form synovial joints. The spinous processes, when seen from the side, are broad; when seen from the end they are narrow, expanding into an enlarged extremity. The heavy superior articular processes bear the mammillary processes; their facets are slightly concave, while those of the inferior articular processes are slightly convex. The synovial joints between the upper lumbar vertebrae for the most part approach the sagittal plane, for the facets of the superior articular processes face largely medially, those of the inferior largely laterally. However, the inferior articular process of the fourth lumbar vertebra tend to be less sagittally and more nearly frontally placed, so that they hook over the superior articular processes of the fifth lumbar vertebra and help prevent the column from sliding forward on the inclined upper surface of the sacrum. There is, in the lumbar region, a transition from a nearly sagittal to a more frontal orientation of the vertebra.

In the fresh condition a typical vertebra is articulated with the vertebra above and the vertebra below through three sets of joints:

1. The zygopophyseal, posterolateral synovial joints formed by the facets on the articular processes
2. A fibrous joint formed by elastic tissue that stretches between the laminae and occupies the posterior space between the laterally lying synovial joints.
3. A cartilaginous joint in the form of a fibrocartilaginous intervertebral disk that firmly unites the bodies of adjacent vertebra while permitting a small amount of motion between them.

Boundary conditions defined by the physical nature of these joints will significantly effect both range and type of spinal motion that can be effected by an individual in both normal and pathological states.