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Lumbosacral iliopsoas muscle
Last reviewed: 04.07.2025
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The iliopsoas muscle (m.iliopsoas) consists of two muscles - the lumbar major and the iliac, which, starting in different places (on the lumbar vertebrae and the ilium), join into a single muscle attached to the lesser trochanter of the femur. Both parts of the muscle participate in the formation of the posterior wall of the abdominal cavity.
The large lumbar muscle (m.psoas major) is thick, spindle-shaped, and originates on the lateral surface of the bodies and transverse processes of the 12th thoracic and all lumbar vertebrae. Situated in front of the transverse processes, this muscle is tightly attached to the bodies of the vertebrae. Then the muscle goes down, crosses the border line of the pelvis in front and connects with the iliac muscle.
The iliac muscle (m.iliacus) is massive, flat, occupies the iliac fossa, and is adjacent to the lumbar major muscle on the lateral side. It begins on the upper two-thirds of the iliac fossa, the inner lip of the iliac crest, the anterior sacroiliac and iliolumbar ligaments.
The iliopsoas muscle emerges from the pelvic cavity (behind the inguinal ligament) through the muscular lacuna into the thigh area and attaches to the femur, its lesser trochanter.
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