My knee hurts and I can't run....

This past Saturday I was trail running in the foothills behind our house and I was about 6 miles into a 9 mile run when I almost fell going pretty fast down hill. I was able to get my left leg under by body to stop the fall but felt instant pain in my hip and knee. I landed in a lunge type position and was shocked that I wasn't rolling down the trail. My knee and hip hurt for another 2 miles but then the pain subsided. The next day I was scheduled for an 18 mile run and ran with a partner for the first 9 miles. My knee and hip began to hurt around mile 8 and by mile 12 (when I was on my own) I started getting worried. By mile 16 there was a stabbing pain in my left knee. My hip pain never got worse and has now gone away but my knee just throbs. So this morning I went to a physical therapist and learned that I have sprained my MCL (I didn't even know you could sprain your knee), I strained/slightly pulled 3 muscles in my lower thigh that strech down to my knee, and I may have torn my meniscus. Best case scenario is that I just bruised my meniscus but that won't be clear until some of the internal swelling goes down. In the meantime, I've been advised not to run for the next short while but instead to bike and aqua jog. I also have 2 weeks of PT scheduled that will hopefully speed up recovery time. As soon as the pain decreases I can begin running again which I am hoping to be sometime next week. If the pain continues the more likely I am to have torn my meniscus and that won't be so great. Just my luck that this would happen 6 weeks prior to the marathon but considering the trauma my knee went through I'm just happy that nothing is permanently damaged! If all goes well I'll be back on my feet next week and will still be able to run the marathon.