Water on the Knee

Hi John How are things now?? I to suffer from Ankylosing Spondylitis. I am 29 and have had fluid on my knee (but no real pain)for 8 years. I have had 3 occasions where the fluid has been aspirated & injections given (steroid) which have offered relief for 3 months at a time but i am told do more damage than their worth. I have had 2 MRI scans and xrays that show nothing is wrong. My doctor has now offered Chemical Synovectomy with Osmic acid injected into the knee joint and a three night stay in hospital to boot which should relieve the fluid for 2-3 years if all goes well. However although my doc says that this procedure is quite common i dont like the sound of it and as far as i can see it is very out of date and can damage the cartilage and bones!!! Has any one ever explained to you why ank spond causes fluid on the knee??? Cheers Steve