Last week we learned about the psoas muscle. You may have heard your massage therapist refer to the illopsoas muscle....the illiopsoas is actually three muscles: the psoas muscle (major/minor) and the iliacus muscle.
All these names make me wish I'd paid more attention in latin class 8/
(N.B: the "Illium" is the big "wing" of bone of your pelvis..)
This iliacus is one of our major "hip flexors". Short explanation: you can lift your knee and a take a step due to these muscles! Pretty important eh?
Unlike the psoas, this muscle does not tie into the spine, so perhaps it's a little less culpable in back pain issues? I really don't know for sure.
The classic kneeing hip flexor stretch (similar to a karate "lunge punch" position) is used to stretch this muscle ..here's a link on how to do this stretch at the livestrong site.
Here's the google body link to this picture so you can play around with the dynamic display.