A very low-tech suggestion since you have back-knee pain: Have you tried lowering your saddle a bit? Back-of-knee pain can be from a too-high saddle. Since yours rotates to the inner knee, I am not sure if that is it, but it would be an inexpensive thing to try. Last fall I had (in the other leg from the earlier ITB syndrome) back of knee + upper calf tendinitis and also had to cut way back on miles, use easy gears, stretch, etc etc for that one (went to a physical therapist). I had to take it easy for about 2 months before I was back to my normal cycling form - but I did come back just fine - slowly - after that.

It's quite a bit of concern that you have such a long event coming up while you are still having such pain. I definitely don't think you have to give up cycling forever as nearly all ailments can be cured, but usually a major part of the cure is to get off the bike for awhile - or at least cut WAY back on miles. You could continue doing more and more damage to yourself if you keep up the miles. I know you won't want to hear this, but if it were me, I would give some serious thought to pulling out of the MS150. You are not a machine; you gotta take care of your body!

Emily