Dirty looking elbows?

No matter how hard I scrub, and how much lotion I use, My elbows are ALWAYS dry and have a blackish tint to them. They get so dry, that they crack open and bleed. I have tried callus remover as someone suggested, but It had no effect. Any other ideas on how to relieve the pain, and discoloration? (I have tried exfoliating cream, and pumice stones)