Same here. I'm only 28 and have quite bad arthritis in my knee - although mine was a result of a serious knee injury.
The only thing that works for me is a steroid injection into the joint; feels horrible when it's being done, but works a treat and means that you can pedal away like mad when out on your bike without all the discomfot the condition brings with it.
Speak to your consultant when you next see him/her - i'm pretty sure that they'll quite happily suggest they do this for you, as you're an active person and it's affecting you quite badly.
Good luck :o)