Nerve to the Major and Minor Psoas Muscles, Anterior View

Description

Arising from the ventral rami of the upper lumbar spinal nerves within the posterior abdominal wall, fine muscular branches from the lumbar plexus track into psoas major and, when present, psoas minor. An anterior-oriented rendering of this region typically places the lumbar vertebral bodies and intervertebral discs posterior to the plexus, with psoas major lying lateral to the lumbar spine and descending inferiorly toward the pelvic brim. The genitofemoral nerve is usually seen piercing the anterior surface of psoas major, while the femoral nerve forms along its lateral border and the obturator nerve descends along its medial margin. Small psoas branches enter the muscle belly proximally, short and segmental. These delicate filaments matter because psoas major is both a key hip flexor and a corridor muscle for retroperitoneal surgery and anterior approaches to the lumbar spine. During lateral transpsoas interbody fusion (XLIF and related techniques), the lumbar plexus lies embedded within psoas major, so appreciating where motor branches course and where larger trunks cluster helps explain postoperative hip flexor weakness, anterior thigh dysesthesia, and the rationale for directional neuromonitoring. Anatomy that looks minor on paper becomes operative. Fast. Suitable applications include lumbar plexus teaching in gross anatomy and regional anesthesia modules, figure support for spine surgery texts discussing the transpsoas corridor, and patient-education materials explaining why certain approaches can irritate the femoral or genitofemoral nerve. It also works well in rehabilitation and sports medicine content when correlating psoas strain, lumbar radicular symptoms, and hip flexor motor deficits. Anatomical accuracy verified by SciePro's Medical Advisory Board.