MusclePosterior abdominal wall
Psoas major
Latin: M. psoas major
Location: Abdomen
View the psoas major in 3DOrigin
Transverse processes, bodies and discs of T12–L5.
Insertion
Lesser trochanter of the femur (with iliacus as iliopsoas).
Action
The body's strongest hip flexor — lifting the thigh in every step and driving the knee toward the chest; also flexes the trunk from supine (sit-ups).
Nerve supply
L1–L3 anterior rami.
Blood supply
Lumbar arteries and iliolumbar artery.
Clinical relevance
A psoas abscess (classically from spinal tuberculosis) tracks down its sheath to the groin; pain on hip extension (psoas sign) suggests a retrocaecal appendix irritating it. The lumbar plexus forms within the muscle.
Educational anatomy reference, not medical advice. About this content.