My Mom Has Been Told She Has Pressure Wounds On

my mom has been told she has pressure wounds on her buttocks. my question is she has 2 small ones very low on her bottom, and then there is red and very inflamed skin that goes all the way up her back to her waistline. she is making a point of not sitting, but will go lay down on her side in bed instead. i thought you had to have pressure against these areas or do you think there is something else going on?