L4 Vertebra

Description

Running through the lateral aspect of the male lumbar spine, the L4 vertebra sits inferior to L3 and superior to L5, with its large vertebral body anterior to the vertebral arch and the spinous process projecting posteriorly. The superior and inferior articular processes form the zygapophysial (facet) joints, their sagittal orientation in the midlumbar region guiding flexion and extension while limiting axial rotation. Intervertebral discs separate adjacent vertebral bodies, and the L5 to S1 lumbosacral junction and sacrum appear inferiorly as the column transitions into the pelvic ring. Alignment is the story. Facet morphology at L4 matters because it sits near the functional hinge between lumbar lordosis and the more coronally oriented facets closer to the lumbosacral junction, a setup that influences segmental stability and load transfer. Degenerative change at the L4 to L5 level often couples disc height loss with facet arthrosis and hypertrophy, narrowing the lateral recess and contributing to L5 radiculopathy, while pars interarticularis defects and anterolisthesis are typically discussed in relation to L5 but are evaluated in context of L4 vertebral alignment and facet competence. A lateral perspective also supports teaching of spondylolisthesis grading and appreciation of shear forces across the lumbosacral joint. Ideal applications include spine anatomy modules in medical and physiotherapy curricula, radiology teaching files paired with lateral lumbar radiographs or sagittal CT and MRI reconstructions, and surgical education materials for posterior decompression and instrumented fusion where facet joint orientation and lumbosacral alignment drive operative planning. It also fits patient-facing explanations of mechanical low back pain centered on L4 to L5 and the lumbosacral junction. Anatomical accuracy verified by SciePro's Medical Advisory Board.