What Causes Cracked Skin On Buttocks,inner Thighs And Knee?

hi ummm I don t know if I say the word right cause I m from Thailand I have a question I have ummm raw cracked skun on my inner thighs , butts (sorry) and a little bit on my knees they re white lines. I have them for years.how can I ease them ?are my inner thighs , butts and knees okay ?thank you very much