I went for surgery for damaged cartilage (August 2012) in my knee and woke up to be told by the consultant that he had also performed a microfracture procedure (patella groove). It needed doing, I saw the pictures, so no issue.
Also told by the consultant to ditch running and take up another sport.
Hard to take as I have a ballot place in the VLM in April 2013.
Physio's view was not that conclusive, build the right muscle groups to protect the patella, start Pilates and work on the core muscle groups and joint alignment and I might get round.
Sold the treadmill, now have a cross trainer and static bike,
Jury's out on the VLM, but just come through a weeks skiing, turned down a click or two so as not to stress the knee to much.
But I have been accepted for Ride London (102 mile cycle ride) in August, so this may satisfy the competitive urge.
Giving up running for good, it's a tough one, but in the long term I do want to walk un-aided for as long as I can.
Good luck with whatever you decide...