For a good introduction to psoriatic arthritis, check out the article at the mayo Clinic website, www.mayoclinic.com/invoke.cfm?id=DS00476.
Lets see if I can link without a mistake. Might be something useful there for you, I haven't read it yet, but they are good. It is a long article: Psoriatic A.
I have arthritis + osteoporosis, mostly in back and hips and legs, but also have that slightly numb, tingling feeling in a couple of fingers and thumb in my left hand.

So far, for me the doctor recommends exercises, and vitamins in addition to Fossamax and calcium-magnesium supplements. Haven't got recommendations on any particular C vitamin yet. I am still being evaluated. My wife uses exercise balls in addition to the vitamins and an inflamation prescription (VIOXX), and it has helped her.

Gargoyle, the vinegar seems drastic- but I am allergic to vinegar and have to avoid it in any form.