I have bad knees, and they scream at me every day when I do 30DS. Ice it, elevate it for a bit, and keep stretching it. I also stretch my hamstrings and quads a LOT more than Jillian says to, and it helps with the knee pain.
Overuse leads to swelling in the joint...warming up and cooling down won't prevent this. If you've been doing high impact exercise, your joints can only take so much. Especially if you've gone from 0 exercise to 100mph in a short period of time...pool work, recumbent bike, and getting the stress off your knee might not be a bd idea...
yeah, i figured my joints were not liking the high impact stuff. I do exercise regularly just not high impact. I do stretch ALOT though. So if the stretchng helps..that is what I will be doing.