Could anyone tell how to clen my dirty knees! I do a lot of yard work and I have small children . So over time my knees have become very dirty looking and dry . I have tried different loitions and cleansers , and although the dryness goes away they still look really dirty!
Any advice or suggestion would be GREAT !

Thanks ;D

Exfoliate or get skin grafts, no, bad idea. Sorry.

Why don't you wear over-knee trousers while working in the garden. If that still does not do the job, you might want to try wearing the knee-protectors that you whould wear while skating.
Or get some tools that allow you to stand up.
I know some farmers who would always rub (hard) soap under their nails to prevent them from getting dirty.
It might be a good idea to rub vaseline on your knees before you start gardening, so the dirt that comes through your hose does not get that deep.
For the dirt that is already in your skin, it will have to grow out. Bathing long and hot will help somewhat, but it will take a few weeks to wear off.

Try body scrub too on your knee that makes it knee scrub :D then put lotion so it would softer...

I do not now if your knees are like my knees but, I spend a lot of time on them, in the summer it is worse from yard work and flower gardens all in shorts, and then the working in the barn again on my knees in the dirt and in the house cleaning, they become dry and all most stained, I have a lufa sponge, I soak in the bath tub, and gently rub it away, it works well followed up with a good moisturizer, if I do not do this I look like I have some funky disease on my knees and ankles, it is gross,

Their knees might not be dirty, they may be like mine; the skin over them is just a slightly different color than the rest of the leg.