“Scrubs are exfoliating creams and can be used if the knee is blackened due to excessive localised keratin build-up, but they should not be used too often and should be tailored to the skin of your knee.
Too many scrubs can kill new skin cells before they can form their own protective film, allowing outside pathogens such as bacteria to enter. It is also important to be gentle when applying scrubs and to ensure that the skin is sufficiently hydrated before application to avoid over-drying and abrading the skin.”