Ripped in 30 users - what else do you do??

I am curious ~ those of you who are doing JM's Ripped in 30 DVD, do you add extra cardio in or just sticking to RI30? I did extra cardio 3 x's per week while doing 30DS, but feel the RI30 is harder and I haven't been getting additional running in. I *want* to, b/c I feel like I'm slacking off by not doing it, but at the same time I'm afraid of overdoing it b/c my knees are already sore! PLUS the scale is FINALLY moving again after being stuck for a few weeks (I know this isn't long enough to really be concerned with, but it's still frustrating!). Anyway, thanks for any advice!