Corri: my PT'ist (7 yr degree) said my symptoms of leg and lower back pain come from my Piriformis muscle being tight or oxygen deprived. I asked about the Psoas muscle but she said the Piriformis muscle had more to do with my symptoms and she could actually feel that some parts of the Piriformis muscle were tight. Maybe both groups regularly or are common causes trouble.
I Find my piriformis gets tight and the psoas get overworked as a result of compensating.
These two muscles were and sometimes are the problems with my back.
Stretching the piriformis along with self massaging it with a tennis ball has helped fix and or keep the pain and stiffness at bay.
Self massage and streching have truely worked for me.