My form is decent on the way up but bringing the bar down, I still tend to keep the bar as close to my body as much as possible so it slides down my thighs and eventually hitting the top of the knee on the way down.

I've always had a bit of bruising in the same area after deadlifts but didn't care for it much since the bruising would subside after a day until I started doing 425lbs for reps and it'd pretty much be bruised for a good week.

I've got a good idea of how to fix the problem but was just wondering, is the bruising serious and could cause problems in the long run or is it pretty much a part of deadlifting like bruised/bloddy shins are?

Bah nothing to,worry about. That's just part of deadlifting. I get bruises on my thighs and my shins have permanent scars running up them. I would also get bruising around my wrists when I would do heavy rack pulls or shrugs with wrist straps. So much so that a lady at work asked if I was like into bondage or something. I said yes, but that the bruising was unrelated.

I enjoy the scars, bruises and callouses from the iron, I just thought that having the same area bruised every week wouldn't be good in the long run for that area lol.

Long pants on DL day FTW

Id be wary of hitting the top of your knee to hard and damaging your knee with the bar, especially if you're doing it weekly, multiple reps of it. Just my gut says that can't be a good thing.

I always wear pants on deadlift days :D

As well as wearing sweat/jogging bottoms usually wear football socks as well. Help protect my shins. Can always tell when I been dead lifting from the sweat marks on my sweat pants where the bar has been in contact with it

when I lower the weight I usually start by pushing my hips back keeping my legs straight lowering the bar until it is at my knees or below then unlock my knees. I'm lifting a lower weight 130kg/286lbs so can probably get away with that. I train in a commercial gym so I try not to drop the weights too loudly :) get enough stares for dead lifting and doing farmers walk as it is, don't want to deafening everyone during dead lifting :)

Deadlifts will make you strong - not pretty!
I've never had issues hitting the knees on the way down. I'd do more of a controlled drop and pull the knees back away from the bar.

Control the bar on the way down until you pass the knees, then let go. Simple.

Dead-lifting bruising your knees makes you manly ;)

Break at the hips, then the knees and the bar will miss the top of your knee. Just think to break at the hips first to begin the descent and the rest will come naturally.

As I'm sure others have said, never let your knees bend until you've bent your hips. Unless you're a really tall guy/have really short arms, the act of bending at your hips will bring the bar at or below your knees, and you won't smash it. You don't really want to have the bar sliding down your thigh on the descent, cause that either means your lower back is bent or your knees bend before your hip bends. If that occurs, then you might want to lower the weight, cause it might mean the weight is too heavy and you're unable to hold it for any appreciable amount of time.

This is actually, iirc, standard procedure for the dead-lift unless you're one of those folks who just drop the weight.

Pants and very loose knee wraps. I didn't worry about it for a long time and I've now developed bone spurs on the front of my tibia just below both knees. It's to the point I can't kneel. Continually knocking the crap out of your knee with a metal object isn't manly, it's stupid. I'm now having to consider surgery to get them removed.

That's what I was fearing of in the long run.

Gonna do what other people suggested and just break at the hips instead of rolling the bar down.