I've had psoriasis since I was a baby. When I was pregnant with DS 10 years ago, it got MUCH worse...gotta love hormones. Since then, I've had some luck with lotions and ointments. Right now I am on Diprolene and it works ok. I also have an OTC tar ointment called MG217 that I've also had good luck with. The horrible thing about psoriasis is there is no cure...once you have it, you have it. It may go into "remission", but you can always get a flare up. I do know that some treatments work great for some and not for others and what works at first can stop working. Some people have to rotate their treatments going from one medication to another when the first stops working only to return to the original one again eventually for some more success...if that makes sense. I was lucky as a child, I only had small spots. Now most of the time my knees are covered and it looks as though I've skinned my knees. All summer I have to explain "what happened to my knees". I have it other places too, but the knees are the most noticable. I don't know if your doctor informed you, but people with psoriasis have a better than not chance of developing arthritis...sorry.
Good luck and if I can help with questions, let me know.