Pronunciation (il-e-o-SO-us) Origin/Proximal Attachment Iliacus: Inner surface of upper iliac fossa anterior inferior iliac spine (AIIS) anterior capsule of hip joint Psoas Major: vertebral bodies of T12-L4 (& discs) transverse processes of L1-4 Insertion/Distal Attachment Iliopsoas tendon to the lesser trochanter of the femur medial aspect of linea aspera Action/Relevance Flex hipExternally rotate hip Innervation Iliacus: Femoral nerve (L2-4) Psoas Major: ventral rami of spinal nerves (L1-4) Notes Iliacus: Large fan shaped m. lying lateral to the psoas. Iliacus portion inserts on lateral side of psoas tendon Psoas: Long thick m passes under inguinal lig | 
