Introduction: The Psoas


  • The iliopsoas is composed of two muscles: the iliacus and the psoas.
  • Some sources will distinguish between the iliacus and the psoas; often, sources are referring to these two muscles together —whether they use the term iliopsoas or psoas.
  • We follow common usage here, using the word “psoas” to mean iliopsoas.
  • In addition, there is technically a psoas major and a psoas minor. Typically, the word psoas refers to the psoas major which “may vary, growing out from T12 or out from the lumbar vertebra… There is also a psoas minor which “originates at T12 and grows into a thin tendon at the pelvic rim. A relic of the human organism’s primordial ancestry, it is thought to be a disappearing muscle as the body evolves from a semi-flexed to an upright being. It is possible to have only one psoas minor or none at all.” (Liz Koch)


  • The psoas muscles are located deep. (Intestines and female reproductive organs are in front of them.)
  • The psoas is a very large muscle, “almost as big as a wrist.”
  • The psoas links the spine to the legs. There is one on each side of the spine.
  • The psoas originates on lumbar vertebrae and attaches at the femur.
  • From the spine, the psoas moves down and forward across the outer edge of the pubis, then traverses back to the lesser trochanter (on thigh).