The buildup of thick and dead skin formed by the friction or pressure in elbows or knees or in ankles causes the skin to turn black. Leaning onto the table using the elbows or kneeling down while you offer prayers can make the skin look dark. It is really embarrassing for women to wear short skirts or sleeveless dresses with black knees and elbows. Black knees and elbows can happen to any person regardless of the color of their skin. Here are few tips to get rid of black elbows and knees, without any pain.