The L4 vertebra is the penultimate of the five (5) lumbar vertebrae, located just above the fixed vertebrae of the sacrum and thus one of the last of the true vertebrae or movable vertebrae in the spinal column. Like the other lumbar vertebrae, the L4 is very large in both the cylindrical centrum (vertebral body) and the vertebral arch in order to support the weight of the body and handle the vertical compression of the spine above it. This puts a great deal of pressure on the cartilaginous intervertebral discs between the relatively flat surfaces of the centrum that form the articular facets of the joints between superjacent and subjacent vertebrae (the L3 and L5, respectively). The nearly horizontal and rectangular spinous process is likewise substantial, in order to counteract the force of strong muscles in the lower back that attach to it. As for the rest of the vertebral arch, it includes short, strong pedicles with superior and inferior notching; thick laminae; and thin, long transverse processes all surrounding a relatively large, triangular vertebral process through which the spinal cord passes safely. Between each transverse process and pedicle there is a superior articular process and an inferior articular process, each with a facet that articulates with the complementary facet of the vertebra above and below the L4, respectively. The L4 vertebra’s transverse processes are noteworthy for lacking transverse foramina, as with the other lumbar vertebrae. Also consistent with the lumbar region of the spine, the centrum lacks external articular facets.