Could keratosis pilaris only effect my elbows knees and thigh? how to treat it?

Yes: KP is most commonly found on the upper arms, thighs, and cheeks, but can be found elsewhere. KP usually gets better with age. You may may find that skin care aimed at preventing excessive skin dryness, including using mild soaps or soap-free cleansers and avoiding hot baths or showers, helps. Also, using skin moisturizers can be helpful. In more severe cases, talk to your doctor about further care