Fourth Lumbar Vertebra L4

Description

Positioned within the lower lumbar column, the L4 vertebra is identified by its large vertebral body anteriorly and its posterior vertebral arch, where the laminae converge toward the spinous process. A lateral projection emphasizes the pedicles, superior and inferior articular processes, and the transverse process extending laterally from the junction of pedicle and lamina. Intervertebral discs separate L3 to L4 and L4 to L5, while the sacrum lies inferior to L5, forming the lumbosacral transition. Clinically, L4 is a common reference level for lumbar puncture planning and neuraxial anesthesia, since the adult spinal cord typically terminates above this region while the cauda equina continues within the vertebral canal. The L4 to L5 motion segment also carries high mechanical load and frequently develops degenerative disc disease and facet arthrosis, patterns that help explain L4 or L5 radiculopathy in the setting of lateral recess stenosis or posterolateral disc herniation. Clear separation of lamina and spinous process also supports teaching of posterior decompression approaches (laminotomy, laminectomy) and why excessive bony removal can destabilize the segment. Use this illustration for gross anatomy lab manuals, spine surgery atlases, and radiology teaching files that correlate bony landmarks with sagittal and lateral imaging of the lumbar spine and sacrum. It also fits patient-facing education on low back pain when you need to point to a single highlighted vertebra without losing regional context. Anatomical accuracy verified by SciePro's Medical Advisory Board.