I've been suffering from knee pain for years. I've had orthoscopic surgery on both knees, and my left one is shot. You can not only feel, but actually hear the grinding of bone against bone, as the cartilege is gone. An MRI this past spring verifies I need a new knee. But the orthopedic surgeon told me to keep up the bicycle riding (either bike or swimming, as both keep body weight off the knees) and come back when the prescription strength Tylenol no longer knocks down the pain and swelling.

Yesterday on a trail ride, I noticed a new vibration and grinding coming from the left front side of my left knee. This is something new, and so far only happened while cranking along on my bike.

Question I have is, if I go ahead with a knee replacement, will I have to be off my bike so long that I lose all my conditioning, and have to start over from scratch - riding to the corner and back and working up from there?