Sacrum

Description

Curving inferiorly from the lumbar spine, the lumbosacral junction is shown in lateral profile with the L5 vertebral body perched on the sacral base, and the superior articular facets of the sacrum aligned to receive the inferior articular processes of L5. The sacrum appears as a triangular, fused segment with its promontory projecting anteriorly, continuing distally to the coccyx. Intervertebral discs separate the mobile vertebrae above, while the sacrococcygeal region marks the transition to the terminal spine. Orientation is clear. Clinically, this side view is the one most often used to explain load transfer and shear at L5 to S1, where spondylolisthesis, pars defects, and degenerative disc disease concentrate in adult males and can be assessed with lateral radiographs. The relationship between the sacral promontory and the L5 body also underpins pelvic incidence and sagittal balance discussions, concepts that guide deformity planning and interpretation of standing spine films. Clear depiction of the sacrum’s superior facets helps teach why facet orientation can influence stability and nerve root risk at the lumbosacral level. Use this illustration for gross anatomy and musculoskeletal modules covering the pelvis and vertebral column, for exam questions on spinal curvatures and the sacrum and coccyx, or for orthopedic and neurosurgical teaching materials introducing L5 to S1 biomechanics and lateral imaging landmarks. It also suits patient education sheets on low back pain where sacral anatomy needs to be named precisely without clutter. Anatomical accuracy verified by SciePro's Medical Advisory Board.