Loose cartiledge floating around inside your knee joint will just make things worse. I would not rush into reconstruction however. I suspect you can do all the running you want without problems. I would at least give a try to rehabilitating the knee without surgery and see how that works. You can always get surgery later, but once you go under the knife, that is it.
Studies show that people who've had knee surgery are prone to arthritis in the knee.
It is not clear if this is a result of the surgery or the knee injury, however. If you do have surgery, make sure to get a good, experienced surgeon. All the studies show that doing a lot of surgeries leads to better outcomes. Don't be afraid to ask how many of the surgeries the surgeon has done and to seek a second opinion.