Psoas Major & Psoas Minor – Anatomy Breakdown

Nov 7

Treadwell, DPT | Muscle by Muscle Series

Watch the Episode

Watch on YouTube: Psoas Major & Psoas Minor – Anatomy Breakdown

In this episode, Dr. Austin Treadwell, DPT breaks down one of the most misunderstood muscle duos in the body — the Psoas Major and its smaller, often forgotten partner, the Psoas Minor.

The Thumbnail for a Psoas Major and Psoas Minor Anatomy Video by Austin Treadwell, DPT covering Origin, Insertion, Innervation, Action, and Clinical Insights

Overview

The Psoas Major and Psoas Minor are deep, central muscles that connect your spine to your lower body — bridging posture, power, and stability. Often labeled the “hip flexors,” they do far more than flex the hip. These muscles influence spinal alignment, pelvic position, and even breathing mechanics.

Clinically, they’re relevant in everything from low back pain to core dysfunction and hip mobility limitations.

Origin & Insertion

Psoas Major:
- Origin: Transverse processes and vertebral bodies of T12–L5
- Insertion: Lesser trochanter of the femur via a common tendon with Iliacus
Psoas Minor:
- Origin: T12–L1 vertebral bodies
- Insertion: Iliopubic eminence

𖤓The Psoas Minor is absent in about 40–50% of people — when it’s there, it acts more as a stabilizer and fascial tensioner than a mover.

Function

Psoas Major:
- Primary hip flexor
- Contributes to lumbar stabilization and anterior pelvic tilt
- Assists with trunk flexion when the femur is fixed
Psoas Minor:
- Weak lumbar flexor
- Tenses the iliac fascia and helps maintain core tone

Clinically, tightness or overactivity in the Psoas can mimic anterior hip pain or contribute to lumbar lordosis and movement inefficiency. Conversely, underactivity or poor control can reduce hip drive and postural control.

Innervation & Blood Supply

Innervation: Branches from the Lumbar plexus (L1–L3)
Arterial Supply: Lumbar arteries, branches from the iliolumbar artery

Clinical & Training Insights

Chronic sitting can shorten the Psoas, pulling the pelvis into anterior tilt and stressing the lumbar spine.
In athletes, the Psoas Major is often under-recruited in favor of rectus femoris — leading to reduced hip drive.
Eccentric control (like slow lowering from a hip flexion position) may improve mobility and reduce anterior hip tension.
Research spotlight: EMG studies show Psoas Major activation increases significantly when the hip is flexed above 90°, underscoring its role in deep hip positions like sprinting or high-knees drills.

Clinical Relevance

Linked to low back pain and pelvic asymmetry
May contribute to altered breathing mechanics due to fascial connections with the diaphragm
A target in advanced pelvic floor and core integration rehab programs

Take the Next Step

You’ve got the anatomy down — now put it into motion.
If you’re a clinician, let’s talk application.
If you’re an athlete or lifter, let’s talk performance.
And if you’re just trying to understand why your hips or back feel the way they do — this is where anatomy meets action.

𖤓 Watch more breakdowns on YouTube: Treadwell, DPT – Muscle by Muscle Series
𖤓 Book a Virtual Consultation: TreadwellDPT.com/appointments
𖤓 Download free PT tools & anatomy resources: TreadwellDPT.com/resources

Much more in store; even more to come.
Stay tuned, stay locked. Treadwell, DPT. 🚀

Austin Treadwell