I believe the Alternative Healing Centre on Aungier St is quite good. You can find a full listing of therapists on www.holisto.com.
Also, I haven't tried it, but there's a a great-looking herbalist place in the Dundrum centre. If you try it, do let me know how you get on.
Finally, you can also contact the CNM (College of Naturopathic Medicine in Grffith College; www.naturopathy-ireland.com) on 01- 2353094. They specialise in herbalism so should be able to recommend a good local therapist.
Im reading a book called the arthritis cure which i bought in Tony Quinns Health shop in Blanch. According to the book using Glucosamine/chondroitin and ASU will help sufferers. Ive had this verified by a man in his late forties who used to play in my club. He started using the Glucosamine and Chondroitin and found that his aching joints improved condition dramatically.
Might be worth looking into! Hope this helps!