Drop the weight and go deeper, IMO. You are barely touching parallel. I'm no pro but that's not deep enough, IMO. It's probably also more dangerous for your knees to stop at parallel, too. Go deep.
I'm 6'3" and go as deep as physically possible. Quads are on my chest and hams are on my calves. Basically I look like an accordion at the bottom, despite taking a closer stance than most at my height. That's with a bad back and hip issues, too. Knees feel great, tho.
This is me at the bottom, high bar:
Also, I like pausing, myself. Not long but just enough to try to get rid of the insta-up. If i don't pause and just reverse direction my back says NO and I drop the weight.
http://i.imgur.com/OkbwR85.gif
MAKE FUN OF MY CALVES ALL YOU WANT, FUCKERS. I'M OVER THEM.