There is a noise familiar to all who have been in the weight room long enough (actually there are lots of noises but let’s limit ourselves to one for today) and that noise is the sound of someone hitting their knee with the barbell.
I think we can all agree that hitting your knee is a bad thing. It hurts andit slows down the lift. So there are a couple of solutions here. First, you could position your shins vertically so that you can lift the bar straight up without risk of hitting your knee. If your body proportions work out, it can be a good solution. However, for lots of us, that doesn’t work. Our stance is such that our knees stick forward or our legs are long enough that our knees stick forward or whatever. So the other option is to push our knees back as the bar rises so that we just barely miss our knee.
Whatever solution you find, make sure the bar doesn’t go forward as you pick it up off the ground. If the bar goes forward then the bar path become inefficient. Another way of putting it is, keep the bar close and moving in as straight a line as possible.