The Untold story of Mighty Psoas Part 1

There seems to be lot of “dysfunctional psoas causing back pain” articles. We like to offer another viewpoint.

How psoas  effects  on posture?   

The answer is a general facilitation along the anterior kinetic chain. The body doesn’t like to be in a position to  stabilize. If it is weak in an action such as flexion, the body will move more into flexion, which gives the illusion of being in a safe position. Lots of questions, and each person has their unique answer. Looking deeper into causation instead of chasing symptoms is a good practice.

                               Don’t just treat what you see, Peel off layer step by step.

The psoas is involved in posture, stability, and breath. The psoas is a multisegment muscle, as it crosses multiple joints from the thoracic lumbar junction through each lumbar vertebrae. The psoas connects the axis of the spine to the appendicular function of the hip. The attachment on the thigh, the lessor trochanter, gives the psoas mechanical advantage in external rotation of the hip. The psoas is a lumbar stabilizer, a hip flexor, and is also a synergist in the breathing .

The psoas is central to movement stability.  However, muscles that cross multiple joints don’t have as much mechanical leverage. Moreover , they are good at  dynamic stability of hip joint.  In the case of hip flexion, the function of the psoas is stabilization of the lumbar while its synergist, the iliacus, generate power .

The psoas is a multi-planer stabilizer that works in a three-dimensional model. The psoas more like to associate with  the quadrates lumborum,(QL). The QL has a fascial compartment just posterior of the psoas(as you can see in fighure). The compartments need to have the capacity to glide across one another , therefore it discreet function can happen in the sagittal, coronal and transverse planes.

In sagittal plane movement the psoas and QL work in ipsilateral pairs on the same side. This is also true for the coronal plane. Though in the coronal plane, while one side is shortening, the opposite side is lengthening. This is called lateral flexion. The function of the psoas in the transverse plane is related to the walking gait. The transverse plane pairing is contralateral.

One side of the psoas is working with the opposite side QL to stabilize the lumbar as the pelvis is moving around the axis of the spine.

The psoas is a primary compartment of the greater lumbodorsal fascia. This fascial sheath connects the torso to the pelvis so that the action of the appendicular skeleton and axial skeleton wind-up and release elastic energy throughout the cycle of the walking gait.

Psoas has its relationship to the breathing pattern. Further, the psoas shares connective tissue with the thoracic diaphragm. This is significant because when the psoas doesn’t play well with the breathing apparatus.

Biomechanics : An overview

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The psoas major  is first and foremost, a muscle of the hip joint . We need to compare its line of pull at the hip joint in each of the three cardinal planes. These actions occur when the lower extremity is in  “open-chain” position. In spite of,  if the foot is planted on the ground and the lower extremity is in closed-chain position, the pelvis moves at the hip joint instead; when the proximal attachment moves instead of the distal attachment, this is called a reverse action . Hence, a thorough examination of the psoas major at the hip joint involves consideration of its standard and reverse actions at that joint.

The psoas major is more complicated because it also crosses the lumbar spine, therefore we need to also examine its line of pull across the spine. However, the psoas major is more complicated because it also crosses the lumbar spine, therefore we need to also examine its line of pull across the spine. As with the hip joint, the spine also allows motion in all three cardinal planes, therefore, our examination algorithym must consider  the possible spinal actions in each of the three cardinal planes. There are many joints within the lumbar spine, each with its own axis of motion; therefore each of these joints must be considered separately. And finally, interposed between the spinal and femoral attachments of the psoas major is the pelvis. Therefore, the pull of the psoas major can affect the posture of the pelvis. Changing the posture of the pelvis can then change the posture of the lumbar vertebrae, which can change the line of pull of the psoas major relative the axes of motion of the lumbar spinal joints and therefore possibly change the action of the psoas major.

All of these factors help to explain why the psoas major can be so challenging to understand. In the following  articles in this series will be an examination of the functions of the psoas major at both the hip and spinal joints.

Stay tune with us for psoas major  Hip joint function in saggital, frontal plane and transverse plane….

REFERENCES :

• Basmajian, J. V. & DeLuca, C. J. (1985). Muscles alive: Their functions revealed by electromyography (5th). Baltimore: Williams & Wilkins.
• Gibbons, S. (2007). Clinical anatomy and function of psoas major and deep sacral gluteus maximus. Published in Movement, stability & lumbopelvic pain: Integration of research and therapy (2 ed.). (Edited by Vleeming, A., Mooney, V., & Stoeckart, R.) Edinburgh: Churchill Livingstone of Elsevier.
• Hall, S. J. (2012). Basic biomechanics (6th). New York: McGraw Hill.
• Hamill, J. & Knutzen, K. M. (2003). Biomechanical basis of human movement (2nd). Baltimore: Lippincott Williams & Wilkins.
• Hamilton, N, Weimar, W. & Luttgens, K. (2012). Kinesiology: Scientific basis of human motion (12th). New York: McGraw Hill.
• Kapandji, I. A. (1974). The physiology of joints: Volume three: The trunk and the vertebral column. Edinburgh: Churchill Livingstone of Elsevier.
• Levangie, P. K. & Norkin, C. C. (2011). Joint structure and function: A comprehensive analysis (5th). Philadelphia: F. A. Davis.
• McGill, S. (2007). Low back disorders: Evidence-based prevention and rehabilitation. Champaign: Human Kinetics.
• Image courtsey : Tech me anatomy, Sequence Wiz

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