[1][2] The psoas minor muscle originates from the vertical fascicles inserted on the last thoracic and first lumbar vertebrae.

From there, it passes down onto the medial border of the psoas major, and is inserted to the innominate line and the iliopectineal eminence.

Additionally, it attaches to and stretches the deep surface of the iliac fascia and occasionally its lowermost fibers reach the inguinal ligament.

[citation needed] The psoas minor muscle is innervated by direct branches of the lumbar spinal nerves.

[6] The psoas minor muscle is considered inconstant and is often absent, only being present in about 40% of human specimens studied.