Did you get an operation/scan or anything after your dislocation? It could be that you've got some soft tissue injury that happened as a consequence, that has so far gone unnoticed. If that's the case then DO NOT play any sport until you get it sorted. It could be the difference between it being fixed, or just removed and leaving you with a f***ed knee for the rest of your life.
As someone who had cartilage problems in the past (which are now fixed, thankfully), I can also recommend glucosamine. Also, the doctors are right in saying you should try and keep the muscles strong around the joint, it takes pressure off the joint itself and if you do need an operation, apparently it makes it much easier both for the surgeon and for your recovery. Things like cycling and swimming are good for this, but don't do anything that will put impact on your knee. I know how tempting it is to go for a kick about, but I have friends who have done that (who subsequently warned me not to) and now have endless problems with it.
As someone who had cartilage problems in the past (which are now fixed, thankfully), I can also recommend glucosamine. Also, the doctors are right in saying you should try and keep the muscles strong around the joint, it takes pressure off the joint itself and if you do need an operation, apparently it makes it much easier both for the surgeon and for your recovery. Things like cycling and swimming are good for this, but don't do anything that will put impact on your knee. I know how tempting it is to go for a kick about, but I have friends who have done that (who subsequently warned me not to) and now have endless problems with it.