Psoas major muscle

The psoas major (/ˈsoʊ.əs/ or /ˈsoʊ.æs/,The word psoas comes from the Greek psoa meaning the “loin region.”) is a long fusiform muscle located on the side of the lumbar region of the vertebral column and brim of the lesser pelvis. It joins the iliacus muscle to form the iliopsoas.

Structure

The psoas major is divided into a superficial and deep part. The deep part originates from the transverse processes of lumbar vertebrae I-V. The superficial part originates from the lateral surfaces of the last thoracic vertebra, lumbar vertebrae I-IV, and from neighboring intervertebral discs. The lumbar plexus lies between the two layers.

The iliacus and psoas major form the iliopsoas, which is surrounded by the iliac fascia. The iliopsoas runs across the iliopubic eminence through the muscular lacuna to its insertion on the lesser trochanter of the femur. The iliopectineal bursa separates the tendon of the iliopsoas muscle from the external surface of the hip joint capsule at the level of the iliopubic eminence. The iliac subtendinous bursa lies between the lesser trochanter and the attachment of the iliopsoas.