One step at a time...Literally!! Like other say, check with your new orthopedic surgeon. As you walk (if there is no pain), I would think you should start by walking further and further. If you have built up to 2-4 miles of walking (with no problems except soreness) you can do the C25K. Take it slowly and build up the endurance and the leg muscles. If the legs can take the pounding of the jogging, you are good to go. Jogging takes different muscles, and with knee replacements, it may be difficult. If you can't jog, continue with the walking or find some other exercise. For many of us, just walking and finishing a 5K if big accomplishment!! I would love to jog...I have a bad back, so I have taken up the bicycle...Never looked back!!