What is the Psoas Muscle?

The psoas (pronounced "so - oz") 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.

This has a number of diverse functions making it a key factor in health. The psoas as a hip and thigh flexor is 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 it optimum. It requires that the psoas maintain 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.

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 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 point, as well as the piriformis, gluteals, hamstrings, and erector spinae.

It 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 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.

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 it shortens 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