The cartilage is worn out in both my knees from arthritis. I've been able to manage the function of my knees and the pain through diet, exercise, and medication. My new surgeon is Dr. Scott Kelly of Duke, and I see him in October for another evaluation. When I last saw him in April, I elected not to have the surgery anytime soon because the function in my legs is still high and I don't have to use a cane. I used to, but I don't now.
A couple of people have told me (no medical professionals) -- "don't wait too long to have your surgery." I guess the reasoning for this is -- well, I'm not sure what it is. And I'm still not ready.
Here's an article from the New York Times: http://www.nytimes.com/2008/05/13/health/13joints.html?_r=0&adxnnl=1&adxnnlx=1374934048-5Dj2wmq6ueOsePeO/RePng
After reading this, I need to decide whether the worn out cartilage alone is grounds for having the surgery. I'll touch base with the surgeon again in October.