My knee has a very dark rough spot that sort of looks like a small bruise. i've had it for so long it never seems to go away. is it dead skin? it's so rough compared to the rest of my knee. i also have very rough dry dark areas around my big toe that is

Dark patch: sounds like dry skin or possible eczema or psoriasis.

Working Skin.: Darken, roughened areas of skin are often seen around joints and areas of high skin motility. They are usually due to multiple layers of shin causing a pigment increase perception. You can always have it evaluated to see if it is something else, but often there is little that can be done.