It used to be that a knee injury could mean the end of an active sports life. However, modern knee replacements are strong and most people can resume normal activity, even "dangerous" sports like skiing, though it may take some time to do.
Do Your PT Exercises
Follow your doctor's prescribed physical therapy regiment after the knee replacement to strengthen the muscles in your leg. Chances are, before knee replacement, you may have been more sedentary due to pain, so you need to improve your conditioning.
Recover fully before hitting the slopes. Only you will know how well your knee has healed. Some people are able to ski within a few months of knee replacement, while others need several years.
Consult with your surgeon before returning to activities like skiing to see if he or she feels your recovery allows it.
Go to a custom ski boot fitter and get custom footbeds made for your boots, and have the boot fitter get your boot properly fitted. The footbed and fitting will help keep your leg in a neutral position and enable better skiing.
Start slowly on the slopes and plan to ski only easy and intermediate runs while you get a feel for how your knee responds.
Pay attention to how your body responds on the slopes. If your knee gives you pain, stop skiing and rest it, as you could potentially reinjure it.