Hi Todd
I'm too late to stop you crossing over to the dark side - you've bought them. I'm a bit of a naysayer on the poles. Partly as a knee-jerk reaction to the marketing. Apparently we can't walk unless we are quadripeds again according to the marketers. We need $100 poles to move around with. I prefer to keep my hands free for other things, and watch my footing.
I agree with the posters that argue if you are going to use them, use them properly. www.sectionhiker.com (nothing to do with me) provides a balanced view on this.
River crossing is a possible exception - in which case a single sturdy pole on the upcurrent side is required.
Now to the constructive stuff... the knees. I too have knee problems from overuse (army). I favor strengthening and conditioning over a knee brace. Check out orthoinfo.org/PDFs/Rehab_Knee_6.pdf, http://www.webmd.com/osteoarthritis/knee-pain-16/slideshow-knee-exercises, and http://orthoinfo.aaos.org/topic.cfm?topic=a00564 Carry a brace with you, but avoid it unless you tweak something on the trail.
Hope this helps