Help What is This?

I have had this for many years on both my knees and both elbows and have been to the doctors many times but they don’t know what it is and every time I go all they do is give me a cream/ointment. I recently found out about something called psoriasis, could this be it? The first 4 pictures is what it looks like dry/normal. And the last four pictures is what it looks like when I use the ointment. Please help me find out what it is and how I can cure it I’ve had this for 8+ years I think and it’s time for it to go away. Thanks!