Hip, leg, and knee

So I was in NYC on business on Monday, and ran on a shady looking treadmill at the hotel. Should have known better because the thing looked older than me, but I was all jacked up with energy because I didn't get to exercise on Sunday. I ended up "jamming my knee about 2 miles into the run. Basically the treadmill changed the speed and incline on the program so dramtically I came down on straigth leg. Since then my hip, leg and knee has felt all out of sorts. My right buttocks hurts, my knee is popping, and the leg muscles are twitching when sitting still. I have run a couple of times since, but shut it down if it starts to feel to painful. Any ideas as to what is going on? I will add that if I kneel on the knee, it pops the knee cap, and it feels a ton better, but it seems to slip again very quickly.