26/08/2026
4 Things You May Not Know About The Psoas Major
Rarely do I get a request to treat a specific muscle. One example is the psoas [major]. Interestingly enough, clients rarely know much about it. Put simply, the psoas major is the primary muscle of hip flexion. Think about the action of raising your knee when you walk or climb stairs. It extends vertically and deep to the abdominal cavity, connecting the medial (inner) aspect of the upper femur to the lumbar spine on the same side.
Now, here are 4 things that even fewer people know. Hint: #4 is a fun fact for you anatomy geeks.
1. Function & Stability
This muscle, working in union with the iliacus as the iliopsoas, is involved in a lot. It helps to rotate the thigh outward, adduct the leg (or pull it toward the midline), flex the trunk (as in doing a sit-up), and even laterally flex the trunk to the same side. Of equal importance, it helps to stabilize the spine and lower back for upright posture.
2. Trained Professionals Should Treat It
Because of its location, the psoas is tricky to treat. One must bypass lower abdominal muscles and organs to apply pressure just inside the anterior surface of the ilium. Entering too low, one can push into the inguinal ligament. Too far medial, one can compress the femoral artery or a portion of the ascending/descending colon. Rushing too quickly can be painful for the client. As a massage therapist, I insist on understanding the qualifications of anyone who attempts this on me.
3. Implications in Breathing
The psoas is connected to the diaphragm (the primary muscle for breathing) via connective tissue called the medial arcuate ligament. Inhalation relaxes tension in the psoas as the diaphragm extends lower into the abdominal cavity. Deep exhalation adds tension as the diaphragm rises toward the lungs. You can test this using the “World’s Greatest Stretch”: inhale deeply as you lunge into hip extension on one side, then exhale deeply as you rotate the opposite arm skywards.
4. Some People Have an “Extra” Psoas
Approximately 40-50% of humans have a vestigial companion to the psoas major called the psoas minor. Even more interesting, the evolutionary drop-off is unstable. A person can have both (bilateral) or only one (unilateral). Fascinating!