Honestly, I've found that throwing the knees from the kneeling position is actually very problematic. In order to deliver a really crippling blow, you basically have to stand up. If you're quick, and your opponent is slow, you can make this work, but otherwise, it's pretty difficult to maintain pressure and (as a result) position control while throwing strikes with the knee.
Both of these are pretty common attacks that I see from freestyle wrestlers, and there's a reason that they're common: they work.
A lot of the time, if you end up straightening his leg out, you're going to be working to pass from there, and that's fine, but I'd rather come up in side-control than come up with legs in front of me, which is why the attack revolves around the hips: so that you're coming up above the legs.
yah I like the first one better because you just circle around and are in crossbody but sometimes the guy's legs are so big I can't get the grip I want for both legs