The Psoas Muscle Resource

What is the psoas muscle?

The psoas muscle is extremely popular and for good reason. It can be involved in many problems and issues that the general population deals with, including lack of core stability, back pain, leg pain, SI joint pain, breathing problems, and the list goes on.

I discuss the psoas in detail in my book Functional Anatomy of Yoga p. 119 (1st ed.) – Get a copy from Amazon if you don’t have it already.

I have put together some important elements to understand surrounding the psoas muscle and its partner, the iliacus muscle. Keep in mind that these two function together and are then known as the ILIOPSOAS Muscle.
psoas muscle yoga anatomy

The psoas is a general term, but most often it refers to the combination of two muscles, the iliacus and the psoas major muscle. Together these two muscles are better known as the iliopsoas muscle. They are linked together because of their common attachment to the femur.

There is one more muscle that contains the word psoas and is worth mentioning briefly. It’s called the psoas minor muscle. You can see it on one side of the image above. As you look at the image above it will be on the right side as you are looking at the image, but this would be the left side of the body, anatomically speaking. Right click and you can open the image in a new window and zoom in to see it.

As it turns out, the psoas minor is absent in approximately half of the population. Not to worry, its function is minimal, so back to the main players.

The Iliopsoas

As I was saying, the iliopsoas is the combination of both the iliacus and the psoas major muscles. They link together toward their bottom (distal) end where they attach to what is called the lesser trochanter of the femur. This means that the muscles cross the hip (acetabulofemoral) joint. Because of their positioning, they are very powerful hip flexors, the strongest in the body in fact. Additionally, this muscle externally rotates the femur from anatomical position.

This muscle is probably the singlemost important postural and structural muscle in the body. There is a long list of reasons why it is so important.

  • It connects the upper half of the body to the lower half of the body
  • It lies on either side of the sacrum and therefore our center of gravity, which means…
  • It is key in controlling big movements of the body
  • It is related to the strength of the spine
  • It can create a strong lordosis (accentuated lumbar curve)
  • It can often be related to back pain
  • It is considered the epitome of the “core” muscles


  • It lies in the pelvic bowl, which is cross culturally the origin of energetic circulation
  • It is related to Uddiyana Bandha (Read my article on this subject).
  • It lies in an area of the body related to emotion, for example “gut instincts” or “butterflies in our stomach”
  • It is related to the fight or flight mechanism – it takes us into a fetal position

Muscular Attachment of the Psoas Major

The psoas major attaches (originates) proximally (above) on the bodies of the vertebrae. The bodies of the vertebrae are the large round bony parts that the disc sits between on the spine. The attachment of psoas major is on the sides of these bony structures.

Attaches proximally to T12 – L4 body of the vertebrae.

As the psoas major heads down on either side of the spine it crosses a total of eight joints, including the sacroiliac joint, before heading forward slightly to drop over the front of the pubic bone, and then finally reach its distal attachment on the lesser trochanter of the femur.

Attaches distally to the lesser trochanter of the femur.

One could easily argue that if a muscle crosses over a joint it can affect that joint. This seems to be true of the psoas major.

The eight joints that it crosses over are:

T12 – L1, L1 – L2, L2 – L3, L3 – L4, L4 – L5, L5 – sacrum, sacroiliac joint, and lastly the hip joint.

The psoas can have an effect on all of the vertebral joints mentioned above. It can either pull the lower ones into a stronger lordotic curve, or, if pulling at the top closer to T12, it can actually reduce the amount of lordotic curve. This seems to depend on other postural issues that might be in play.

Its relationship to the sacroiliac joint (SI joint) is also extremely important. It is the relationship between the psoas and the pirformis muscle that most directly creates a muscular balance at the sacroiliac joint. Ligaments that attach at the SI joint and other postural aspects can be part of an SI issue, but muscularly, the balance of tension between these two muscles is critical for balance at the SI joint.

Muscular Attachments of the Iliacus Muscle

The iliacus is sort of the lesser known part of the word psoas. This muscle is dedicated to moving the femur at the hip joint. Short, thick, and powerful, it’s the unsung hero of the psoas story and creates the powerful hip flexion that we need for so many activities.
iliopsoas attachment
It attaches inside the pelvic bowl onto the inside of the ilium. The ilium is the large flat bone that sticks up on either side of the pelvis. The attachment of this muscle defies one’s normal idea of how a muscle attaches to a bone.

In the case of iliacus, the tendinous attachment is actually under the “muscle” itself. It’s not a long round tube of tissue in the way we normally think a tendon is.

Attaches proximally to the iliac fossa (depression).

Attaches distally to the lesser trochanter of the femur.

Back Pain and the Psoas Muscle

People often associate back pain with the psoas. Common thoughts are that the psoas is either too weak and not supporting the back, which leads to pain, or that the psoas is too tight and is creating a strong lordosis, which is causing back pain. Both are possibilities.

What the variability with regard to psoas and back pain shows more than anything, is the need for a good evaluation of all the potential contributing factors to back pain. Some of those may be: lack of exercise, stress (particularly related to money), sitting for too many hours without stretching, or a big belly – every 10 pounds of weight in the abdomen translates into approximately 30 pounds of pressure on the low back.  The list could go on.

One element that can be overlooked is quite simple, the muscles of the back are tired, fatigued and pissed off. Many people seems to be after the more complicated possibility. They have heard of the psoas and therefore gravitate to it as if it holds the key to every problem in the body. This is a mistake. Even if it is tight, it’s probably still only one component of many that are actually causing problems for someone. Again, good evaluation is the key.

Let’s not forget about trigger points. My favorite reference site for trigger points is

I especially like this site because they use images from the medical textbook written by Dr. Janet Travell (who was John F. Kennedy’s physician) and Dr. David Simon. Although it’s expensive, this is an exhaustive resource that I have poured through numerous times and have learned alot from. If it seems too daunting, you may consider getting a flip chart that is all images.

Trigger points from these two muscles, as you can see below, can refer pain into your lower back. So, you should keep trigger points in mind as a potential culprit in back pain. Did I mention that good evaluation is the key? I think I did.iliopsoas trigger points yoga anatomy

Psoas Awareness Video Clip

Before too long I’ll try to add a video on how find your own psoas and how to stretch it.

(Below) David Keil Leading simple sun salutations at a yoga anatomy workshop (Stillpoint Yoga London). Use the image above as a mental image. Try to move with intention from where you would imagine this in your body. You can also download the psoas video clip from the DVD here.

Article by Liz Koch copied from Yoga Journal Website

Release Your Psoas

These 10 poses can help you create the internal awareness needed to access the muscle that is the key to your structural ability.

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