Post opperation rehab is much better with good fitness going in to the opp. If the pain is on impact only then cycling and swimming may be just the thing. My partner was out of running for 4mths due to a foot injury that was slow to respond to treatment and it's only the swimming and cycling that kept him sane, not a miserable sod and me from killing him!!! Is the problem front, inside, outside, back of knee? I really do hope that it can be fixed without the need for surgery. This is a great little link that I often use for research purposes http://www.runninginjuryoracle.com/.