Posterior Superior Iliac Spine's Structure, Lateral View

Description

Posterior superior iliac spine (PSIS) forms the palpable posterior termination of the iliac crest, and in this lateral perspective it appears as a distinct bony prominence projecting posteriorly from the ala of the ilium. The iliac crest sweeps superiorly and anteriorly from the PSIS, while the posterior border of the ilium descends inferiorly toward the posterior inferior iliac spine and the greater sciatic notch. Medial to the PSIS lies the roughened iliac tuberosity, the auricular surface for the sacrum sits just anteromedial to it, and the lateral surface of the ilium remains visible as a broad, slightly concave expanse. PSIS is a constant surface landmark for orienting the posterior pelvis, and this illustration makes its relationship to the iliac crest and sacroiliac region easy to teach without the distraction of overlying soft tissue. Clinically, palpation of the PSIS guides assessment of pelvic tilt and asymmetry and is frequently referenced in low back pain workups where sacroiliac joint dysfunction, ankylosing spondylitis, or degenerative SI arthropathy is suspected. The fixed lateral view also supports procedural planning, since posterior SI joint injections and radiofrequency targets are commonly discussed relative to the PSIS, the adjacent sacral ala, and the posterior ligamentous complex. A hard landmark. Use this illustration in gross anatomy and musculoskeletal anatomy curricula when introducing pelvic osteology, or in orthopedic, sports medicine, and pain medicine materials that need a reliable reference point for sacroiliac palpation and intervention. It also fits well in atlases and patient-facing explanations of SI joint pain patterns anchored to the posterior iliac crest and PSIS region. Anatomical accuracy verified by SciePro's Medical Advisory Board.