Psoas Major (Iliopsoas / Hip Flexor)
Gluteal & Hip · Lower Limb
The psoas major is a long, thick muscle of the posterior abdominal wall that is the chief flexor of the hip. It arises from the transverse processes and bodies of the T12 to L5 vertebrae and their intervening intervertebral discs, then descends across the pelvic brim to insert, together with the iliacus, on the lesser trochanter of the femur; together these two muscles form the iliopsoas. Acting on the hip it produces flexion, and acting on the trunk it flexes and laterally flexes the vertebral column. It is supplied directly by the anterior rami of the lumbar nerves (L1, L2, L3).
Origin, Insertion, Action & Nerve
Origin
Transverse processes and bodies of T12–L5 vertebrae and intervertebral discs
Insertion
Lesser trochanter of femur
Action
Flexion of hip; flexion and lateral flexion of trunk/vertebral column
Nerve
Anterior rami of lumbar nerves (L1, L2, L3)
Attachments explained
The Psoas Major (Iliopsoas / Hip Flexor) is defined first by where it attaches. Its origin is the more fixed anchor, usually the proximal or more stable end that stays put during contraction, while its insertion is the more mobile point that is pulled toward the origin when the muscle shortens.
Origin
Transverse processes and bodies of T12–L5 vertebrae and intervertebral discs
Insertion
Lesser trochanter of femur
Action & function
When the Psoas Major (Iliopsoas / Hip Flexor) contracts, it produces the following movements: Flexion of hip; flexion and lateral flexion of trunk/vertebral column.
As part of the Gluteal & Hip group of the Lower Limb, it works alongside neighbouring muscles to generate smooth, coordinated movement and to stabilise the structures it acts on.
Nerve supply & clinical relevance
The Psoas Major (Iliopsoas / Hip Flexor) receives its nerve supply from the Anterior rami of lumbar nerves (L1, L2, L3). This nerve carries fibres from spinal segment(s) L1, L2, L3.
Because a muscle can only contract when its nerve is intact, injury to the Anterior rami of lumbar nerves or to its spinal roots (L1, L2, L3) can weaken or paralyse the Psoas Major (Iliopsoas / Hip Flexor), impairing the movements it normally produces (flexion of hip). This is why knowing the innervation is central to localising nerve lesions in clinical practice.
How to study the Psoas Major (Iliopsoas / Hip Flexor) (the OIANS method)
Learn the psoas major as one half of the iliopsoas, the dominant hip flexor. Trace it from the lumbar vertebrae, over the pelvic brim, to the lesser trochanter, and its flexing action on both the hip and the trunk becomes a single logical consequence of that long path bridging spine and femur.
Note the unusual nerve supply as its distinguishing feature: unlike its partner iliacus, which is on the femoral nerve, the psoas major is supplied directly by anterior rami of the lumbar nerves (L1, L2, L3). Its close relationship to the lumbar spine also explains why it is used clinically as a landmark and why an abscess can track along it.
Frequently asked questions
Where is the Psoas Major (Iliopsoas / Hip Flexor) located?
The Psoas Major (Iliopsoas / Hip Flexor) is a muscle of the Gluteal & Hip group, located in the Lower Limb.
What is the origin of the Psoas Major (Iliopsoas / Hip Flexor)?
Transverse processes and bodies of T12–L5 vertebrae and intervertebral discs
What is the insertion of the Psoas Major (Iliopsoas / Hip Flexor)?
Lesser trochanter of femur
What movements does the Psoas Major (Iliopsoas / Hip Flexor) produce?
Flexion of hip; flexion and lateral flexion of trunk/vertebral column
What nerve supplies the Psoas Major (Iliopsoas / Hip Flexor)?
Anterior rami of lumbar nerves (L1, L2, L3)
Is the Psoas Major (Iliopsoas / Hip Flexor) free to study in OIANS?
The Psoas Major (Iliopsoas / Hip Flexor) is always free to browse. Its full origin, insertion, action and nerve details are open to everyone in the Muscle Directory. Quiz and Flashcard practice for the Lower Limb is part of the one-time Lifetime upgrade, though; only the Upper Limb decks are free to test yourself on.
Related muscles
Study the Psoas Major (Iliopsoas / Hip Flexor)
Test yourself on Lower Limb muscles with interactive quizzes and flashcards in the free OIANS app.
Quiz yourself → Flashcards Open the OIANS app
Browsing is always free. A one-time Lifetime unlock adds every region's quizzes, flashcards, progress tracking and explore tools.