Smokers, in general, know that smoking is bad for your health. They may even say they don't want to hear it anymore.
But most smokers don't know the extent to which smoking can have effects on all aspects of health. Recent research has looked at multiple studies of various types of knee ligament and cartilage surgery--arthroscopic knee surgery, ACL reconstruction,etc--and the effect of smoking on the results of surgery.
Would it surprise you to know that smokers who had these surgeries did worse than their non-smoking counterparts? That means if you smoke, you shouldn't expect to do as well if you have a knee cartilage or ligament tear... Just another reason to consider quitting.
Source: "Smoking and Knee Surgery" AAOS Now, November 2012. Page 17.