Psoas Major Muscle Beneath the Skin, Anterior View

Description

Running along the anterior lumbar spine, the paired psoas major muscles are exposed beneath the skin as fusiform columns descending from the lateral aspects of the vertebral bodies and intervertebral discs toward the pelvic brim. Each belly lies deep to the rectus abdominis and the lateral abdominal wall, occupying the posteromedial abdominal compartment before passing inferiorly over the superior pubic ramus to join the iliacus in forming the iliopsoas tendon. Iliacus fills the iliac fossa lateral to psoas, and together they course anterior to the hip joint toward the lesser trochanter of the femur. Superficial landmarks of the anterior trunk remain in view. Anterior presentation of psoas major matters because it frames the relationship between hip flexion mechanics and the structures clinicians worry about in the retroperitoneum, including the lumbar plexus embedded within the muscle and the femoral nerve emerging at its lateral border. Pain and weakness patterns in L2 to L4 radiculopathy, psoas hematoma (for example in anticoagulated patients), or psoas abscess can be taught cleanly when you can trace the muscle’s origin on the lumbar vertebrae and its distal trajectory toward the hip. A key teaching point. The muscle’s proximity to the anterior column also explains why hip flexion can aggravate symptoms in lumbar spondylodiscitis and why surgeons use psoas splitting or transpsoas corridors in lateral lumbar interbody fusion, accepting plexus risk in exchange for direct disc access. Use this artwork in gross anatomy and kinesiology courses to clarify iliopsoas anatomy, in pain medicine and orthopedics teaching files to discuss femoral neuropathy and hip flexor strain, or in surgical education materials covering retroperitoneal and lateral lumbar spine approaches. Anatomical accuracy verified by SciePro's Medical Advisory Board.