Posted by Steve Middleton, MS, ATC, CSCS, CES, CKTP
According to body workers, the psoas is an integral muscle in low back pain and posture. However, its function tends to be misunderstood. Most clinicians want to stretch and lengthen the muscle yet, in most individuals, it tends to be tight from being overstretched.
To review the anatomy, it is the only muscle that connects the spine to the lower extremity, originating from the transverse processes of T12-L5 and extending to the lesser trochanter of the femur (figure 1). Its roles are defined as being to create hip flexion when the trunk is stationary playing a role in ambulation. It also creates trunk flexion when the hip is stationary playing an integral role in posture.
The issue arises when we sit for a period of time; the compression creates adhesions in the gluteal fascia. This can be worsened unilaterally when wallets or cellphones are placed in the back pocket. These adhesions create fascial shortening that pulls the femur and hip into extension. As the femur moves into extension, the overstretched psoas begins to feel tight.
Looking at people from a seated position (figure 2), the majority migrate to a posterior pelvic tilt. The common misconception is that this occurs due to shortening of the psoas. What happens is that the aforementioned fascial adhesions of the gluteals limit hip flexion. As hip flexion becomes limited, the pelvis moves into a greater degree of posterior rotation to compensate during the movement.
As this occurs, the psoas loses its ability to maintain trunk alignment. In this event, the rectus abdominis becomes compensatory to maintain a somewhat erect position. However, due to the pull of the rectus abdominis, it is unable to facilitate hip flexion or overpower the dysfunction of the gluteals so it instead increases trunk flexion, specifically thoracic kyphosis, due to its attachment on the 5th ribs (figure 3).
To correct the issue of posture requires lengthening of the gluteus fascia through manual means: myofascial release, instrument assisted soft tissue mobilization and/or post-isometric relaxation. Once adequate length has been gained, proprioceptive neuromuscular facilitation techniques should be utilized to re-educate the psoas in proper firing to facilitate hip flexion. As the hip function improves, normal tone should be restored to the rectus abdominus as it becomes less active during sitting posture.
However, more direct manual treatment to lengthen the abdominal fascia and restore appropriate thoracic extension in more chronic conditions.