Hello, new to this forum but have found it very informative. I have had both knee's replaced.. the right one 5 years ago and the left 4 years ago. Cycling is a great excercise for post knee replacement. Having them replaced did not slow down or hamper my riding one bit. I continue to ride my road bike thousands of miles a year as well has mountain bike. The most important thing after you have your replacement surgery is to get active. By active I mean get up and start moving right away. Do all your physical therapy no matter how much it hurts (and it does hurt , not going to lie). But it is so so important to not let the scar tissue tighten and restrict you range of motion. The more you stretch and preform the recomended excercises post operation the better your quality of motion going forward.