ohhhh........very interesting! Don't you hate it when a doctor says this
Now we are getting somewhere! The MRI is a welcome opportunity to either find the problem, or reassure you that time will heal. The psoas starts as high as L1-2, goes along the side of the spine and inserts into the lesser trochanter of the hip. It pulls the leg up or flexes the leg at the hip and is a weak external rotator of the leg. It gets it's innervation from L2-4 so if you pushed a disc out at that level on the affected side, it could cause your weakness. The importance of this is that you may need and MRI that goes from L2 down to just below the lesser troch of the proximal femur.
Here's some questions - Do you have a fairly arched lower back (the MD may say accentuated Lordosis - comes from the fact that most rich Lords had big bellies that caused them to have arched backs in order to counter balance their Yorkshire pudding gut!) If the back is arched, the psoas gets short, and may predispose you to strains. To stretch you have to pull the leg back and press the pelvis forward and flatten the lower back. It's not easy to do at first, and the PT can really help you with this.
The disc is an interesting possibility (hope I'm wrong). Your post about the pain said something about burning or electric pain and you get numb when sitting for long periods of time. That's what I remember - too lazy to open a new window and go back and read that post before sending this. The other possibility is that you ripped the muscle "slap off" the lesser troch (I take care of many farmers and I love it when they say "slap off") That would explain the large amount of bruising.
Anyway, sounds like you are on the way to sorting things out and getting a solution.
Perry aka Dr B
PS - thanks for the invite to RS III - I have been tempted since the first go around.