Ilio-Psoas Syndrome

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What is the Psoas Muscle?

The number of problems caused by the psoas is quite astonishing.

The biggest factor in back and hip pain is the psoas muscle. Many believe the psoas muscle is the most important muscle in the body. The number of problems caused by the psoas is quite astonishing. These include: low back pain, sacroiliac pain, sciatica, disc problems, spondylolysis, scoliosis, hip degeneration, knee pain, menstruation pain, infertility, and digestive problems. The list can also include biomechanical problems like pelvic tilt, leg length discrepancies, kyphosis, and lumbar lordosis.

The psoas (pronounced "so - az") primarily flexes the hip and the spinal column. At about 16 inches long on the average, it is one of the largest and thickest muscles of the body (in animals it's known as the tenderloin). This powerful muscle runs down the lower mid spine beginning at the 12th thoracic vertebrae connecting to all the vertebral bodies, discs and transverse processes of all the lumbar vertebrae down across the pelvis to attach on the inside of the top of the leg at the lesser trochanter. The lower portion combines with fibers from the iliacus muscle, which sits inside the surface of the pelvis and sacrum, to become the Iliopsoas muscle as it curves over the pubic bone and inserts on the lesser trochanter.

What is the function of the psoas?

The psoas has a number of diverse functions, making it a key factor in health. The psoas functions as a hip and thigh flexor, which makes it the major walking muscle. If the legs are stationary the action of it is a bend the spine forward; if sitting, it stabilizes and balances the trunk. The lower psoas brings the lumbar vertebrae forward and downward to create pelvic tilt.

When we think of smooth, elegant and graceful movement in dancers and athletes we are looking at the psoas functioning at its optimum. It requires that the psoas maintains the pelvis in a dynamically neutral orientation that can move easily and retain structural integrity. This creates positions of the spine that require the least muscular effort.

What are the common pain symptoms of the psoas?

When the muscle becomes contracted due to injuries, poor posture, prolonged sitting, or stress, it can alter the biomechanics of the pelvis and the lumbar, thoracic and even cervical vertebrae. Typically a dysfunctional psoas is responsible for referred pain down the front of the thigh and vertically along the lower to mid spinal column. Trigger points are found above the path of the psoas on the abdomen. Frequently the quadratus lumborum muscles develop trigger points, as well as the piriformis, gluteals, hamstrings, and erector spinae.

The psoas can torque your spine to the right or left, pull it forward and twist the pelvis into various distortions. Frequently one psoas will shorten and pull the spine and/or pelvis to our dominant side. The distortions of the spine and pelvis can also show up as a short or long leg. This all results in scoliosis, kyphosis, lordosis, trigger points, and spasms in back muscles trying to resist the pulling of the psoas.

It can also pull the spine downward, compressing the facet joints and the intervertebral discs of the lumbar spine. The pressure can cause the discs to degenerate, becoming thinner and less flexible. This degeneration makes the discs more susceptible to bulging or tearing, especially with twisting and bending movements.

What keeps the psoas in contraction?

The psoas will stay contracted because of postural habits and trauma. The way we stand, walk and sit can distort the psoas. If we walk or stand with our chin in an overly forward position the muscle will tighten. Sitting through much of the day at the office, car or elsewhere causes the muscle to shorten to keep us bio-mechanically balanced in our chairs. Over time we develop a "normal" way of holding the psoas that is dysfunctional.

Unresolved trauma can keep the psoas short and reactive. This is a primary muscle in flight, fight, freeze or fear responses to danger. When survival is at stake, it propels the body to hit the ground running. When startled, it ignites preparation of the extensor muscles to reach out (grab hold) or run. Until the psoas is released the muscle may stay contracted and go into further shortening and spasm very easily.

What is the Iliacus Muscle?

Iliacus connects with the psoas muscle to form the iliopsoas muscle.

The Iliacus is a flat, triangular muscle, which fills the iliac fossa.

It arises from the upper two-thirds of this fossa, and from the inner lip of the iliac crest; behind, from the anterior sacroiliac and the iliolumbar ligaments, and base of the sacrum; in front, it reaches as far as the anterior superior iliac spine and anterior inferior iliac spine, and the notch between them.

The fibers converge to be inserted into the lateral side of the tendon of the Psoas major, which contributes to flexing the femur anteriorly onto the pelvis. Some of the iliacus fibers may reach the body of the femur, for about 2.5 cm. below and in front of the lesser trochanter.

The Iliacus is sometimes considered a part of the Iliopsoas group of hip flexor muscles.

This muscle is innervated by the anterior branches of the Femoral nerve (anterior branches of L2-3).

Working synergistically with the Psoas in gait (walking) and evaluation for low back pain, careful attention is placed on the slightly different spinal innervation from L4 with the psoas and a more horizontal action (leg further out).

A Bigger Psoas Perspective

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