Thank you for your question. There are no treatments or cures that will lighten the skin completely to your natural colour, nor permanently. As this skin is elastic and used often with regular movement, darkening of the skin is common. I would recommend combination treatments for pigmentation in areas such as knees and elbows. This would include a home care regime of, for example, Luminesce from Lamelle and in-clinic treatments of chemical peels such as Mesoestetics Melanostop or Cosmelan, dependant on your skin type and severity of the pigmentation. Multiple treatments would be recommended and requires use of SPF on a daily basis and limiting sun exposure to the area.