Its been brought to my attention that as I descend in the squat and reach the bottom my left knee drifts inward. Any advice on how to correct this would be appreciated. In the video i am practicing form on the box squat and the knee drift can be seen, but this problem was detected while doing regular squats as I rarely do box squats.
Side View
Front View
Holy slow squat! Reminds me of a certain superfreak, haha… 
Try doubling a miniband around your legs and push out against it when you squat. Also have someone queue you when squatting. Helps when your knee drifts and someone screams KNEES OUT at you…
Ralf,
I watched the video carefully and it looks like near the bottom of the squat your entire lower body is twisting clockwise (from a top view). I would say their is probably some flexibilty issue you have to work on so that you can descend without twisting. I suspect something on your right side is tight.
I’m gonna agree with seattle there, looks almost as if you’re twisting is coming from the hips.
I know you say you don’t do box squats, but if you are going to do them, don’t relax on the box.
make it go … outwards instead?
It could be a weakness of your adductor. You could try squats with different feet stances.