39 yr old active woman with arthritis. Diet/exercise ideas? Meds,Glucosamine,Synvisc or Hyalgan injections?

I was in my doctor's office and saw pamphlets for Synvisc injections for the knees. My doc said it would probably help me. Have been annoyed about my diet and exercise regimen,too. I'm 5',small frame and I weighed 110 pounds 2 yrs ago,creeping up to like 135 now, but lately I can't find any exercises I can do without suffering a great deal in my joints afterward.My doc said stairs and elliptical machines are out for me (knees too bad) Anybody have any input for me, on any of this, I'll be grateful. Also, if anyone has been thru the mill with the arthritis meds, what do you find works well ? (any thoughts on Glucosamine compounds?)