Was changing the rear brakes on our 02 Rendezvous when I noticed that the area connected to the upper control arm is not secured. I could move the rotor back and forward a couple inches.

I could see that the knuckle bushing is worn. Would a new bushing possibly fix this, or am I probably looking at something else?

Post a picture of what your talking about.
Or even better a video showing what your talking about.

Got some major things going on right now, but as soon as I can look at it again, I'll post a pic or vid.