Will I have to give up kickboxing because of arthritis?

My GP told me today I have arthritis in my ankle - bit shocked as I'm only 24, didn't really take in anything he said at the time other than a change in my lifestyle, (I'm not overweight, so i presume he was talking about my physical activity) so I came home and got on the net. I am worried that I will need to give up my hobby for good to prevent further damage. Does anybody else think i should just carry on doing what i love or sub to old age before my time. I have always been active and dread the thought of getting fat and lazy lol.