Suggest Treatment For Dark Skin On Knees

I have had bruised looking knee caps for as long as I can remember. Prob. from scars when I was a kid and playing ball in high school. I am white so it shows up a lot. They aren't painful just annoying that they always look like I hurt my knees. What can I do to lighten them to my regular skin color???? I'm tired of people asking what I did to my knees. Help please!!!!