Convinced I have PA. Very scared - please help

I am a woman of 55. Eight months ago I was diagnosed with severe PPP, scalp and nail psoriasis. It's beginning to clear on my hands and feet but the nail impact has been severe and I have lost all 20 of my finger and toenails. All I have left are short yellow stumps. Six months ago I developed an agonizing pain in my right knee. My GP gave me a steroid injection and this eased it but then I began experiencing the same pain in my left knee. Again I was given a steroid injection. A month ago I developed dreadful pains in my right heel which has been diagnosed as achilles tendonitis. Basically, I am losing my ability to walk. The pain in my heel is so bad that I can only manage about 400 yards. I have had XRays, bloodwork and an MRI scan which showed a torn miniscus (cartilige) on one knee. My derm is adamant that I do not have PA and that my symptoms are due to torn miniscus and can be fixed by surgery - she told me I would have swollen fingers and or toes if I had PA. My instinct is that this is rapid progression PA - especially due to the severity of my nail impact. My life is getting narrower and narrower as I can hardly walk and can no longer go to many of the places I enjoy as I struggle to use public transport. Today I have noticed a painful swelling on my palm at the base of my index finger that has come up overnight. I would really love to hear what other members think. My instinct that this is PA is so strong yet my rheumy (and a physio) I saw last week are adamant that it isn't. My derm prescribed Ciclosporin last week but haven't taken it yet as worried about the side effects of immunosuppressing drugs. But coming to the conclusion that any side effects would be a walk in the park compared to only being able to hobble a short distance. Please help or share your experiences. I am very scared that I seem to be becoming disabled very quickly. Thank you all. REPLY