Sorry to read this but I have to hop in here .. your story sounds like mine about 20 years ago ...
Long story short, when I was 18 I was told the same thing, cartilage above talus and below tibia was gone from playing soccer and too many sprains to count and that I'd have to limit my activity. Didn't really know what that meant so really scaled down on soccer a bit until 4 years ago when I went cross country skiing and really turned my ankle, knocking a chunk of bone out of my talus with the bottom of my tibia. 4 surgeries in 3 years later, I am still having problems with pain and walking and am facing possible permanent disability and a definite ankle replacement in 10-15 years.
Check out ankle OCDs, osteochondral lesions to read what the next step is in your injury if you continue to 'pound' on your ankle. I wish someone told me this when I was 18 and I wouldn't be 41 and not able to walk now .. unfortunately this is nothing to play with and you have the oppty to not do further damage ..
The foot problems section has a lot of into on ankle OCDs which again is a step beyond what you have now, but might be facing years down the road.
Sorry to be so blunt, you can probably hear my frustration with my injury ...but if I could help just one person not go through what I did/am ...