The fascicles of the psoas major are approximately similar in length throughout the lumbar spine and have a unipennate fiber orientation. Muscle fiber length within the anterior fascicles ranges from 3 to 8 cm and 3 to 5 cm in the posterior fascicles.7 The fascicles are oriented inferolaterally and come together as a common tendon which descends over the pelvic brim and shares a common insertion with the iliacus muscle on the lesser trochanter of the femur.