Hey Kim,
I can't believe you asked for a cortisone shot!! I'm terrified of needles, so I'd avoid that option if at all possible. On the other hand, I think it's a testament to how much pain you've been in and how effective the hip shot was. I do hope that your knee pain is temporary and that icing it works.
As for XT, add me to the chorus of voices recommending the bike (maybe spinning classes?) and elliptical. My gym just got some nifty ARC trainers that are a hybrid between ellipticals and stair climbers. They allow your natural hip movement to dictate the machines movement, so you can do more of a run (elliptical) or a climb (stairs) without the impact. Let me tell you, it's quite a workout--a bit odd until you get used to it, but good. If your gym (can't remember if you belong to one, now that I think of it) has an ARC trainer I suggest trying them.
Anyway, I hope you're doing well overall. Please know how much I admire your persistence and dedication to running.