I've started using deadlifts for lower body work a few months ago and, despite having read a lot of descriptions and watched all the videos I can find, I think I am doing something wrong. When I deadlift, I find that the bar keeps kitting my shins and knees, both on the way up and on the way down. This occurs even when I use very light (warm-up) weights. I am trying to keep my spine straight, proper bar position, and pushing through my heels, but this seems to cause the bar to want to go through my shins on the way up, and to "clip" my kneecaps on the way down. (The result is a lot of bruising, and chunks of missing shin skin.) This forces me to lean forward somewhat to allow the bar to clear my knees, which means I end up using my lower back when the bar is quite near the ground, rather than at the top half of the lift. I am hoping that this is a sufficiently common problem that someone might be able to discern what I am doing wrong from this description and point out my error. So my question is this:
What is wrong with my deadlift technique that might be causing me to bruise my shins and knees like this?