Well, the SI issues are secondary due to you favoring one side vs. the other, and will keep going out due to compensating for the injury. Even though it doesn't seem to help now, keep stretching the ITB, it will be aggravated with any knee injury and as long as you can keep it from contracting more it will help in the long run. Rectus fem. work will feel good right now because it is having to stay in a lengthened position, but you also have to make sure that gastroc or the hams don't shorten. But mainly I would definitely go for the orthopedic consult and an antinflamitory to be able to get down to what the issue is (but don't let them give you a cortisone injection!!!). I would go especially if you can't fully extend your knee, it could be an ACL issue. My gross anatomy teacher did tell us that there really isn't anything surgically they can do for popliteus, that gastroc and the hams will take over for the action. So you just have to work on keeping them strong and at proper length.
As for myself, I am also an EMT, I was lifting a patient, my knee buckled and hyperextended VERY badly. I knew something was wrong, it didn't hurt right away yet it didn't feel right either, but later on in the day it just got stiff and by the next day had blown up to 2x its size. I ended up having major compensating issues in the hip from circumducting in order to walk. I did 2 months of PT and decided that it wasn't getting any better and opted for surgery, which I am glad I did due to the true injury not appearing on the MRI. I would have gone back to work and really hurt myself. So then another 6 months of PT after that, off for a month and then back on for 2 more. Then a year and a half later went back for a 2nd procedure to get rid of the scar tissue that had built up. My MD originally thought it was the popliteus due to the fact that I also had lateral pain and there didn't seem to be any give when he did the anterior draw test (which with the damage should have had some give). But before the injury I always seemed to have ITB issues from years of sports, and having valgus knees. I ended up going to MT school 2 months after the surgery, massage made it feel sooooooo much better. Having my ITB and my Anterior Tibialis worked on is excruciating but it is needed, and having all aspects of my leg pettrisaged really makes it feel better. Also if you work on the male tonification point (I can't remember if it is ST34 or ST36) but it is right in the tendinous area that connects the Tib/fib. I have found that it will help relieve some of the discomfort.