Hi Ncmom! The CTX series does have a good amount of high impact intensity during the cardio segments. You can lower your step height and/or take the jump out of some moves and replace it with another high intensity move that is more comfortable for you. Probably the best thing to do at this point in time is to watch the 10 minute film clips of each of these workouts and see if the impact is something you will be able to do or enjoy modifying.
Good Luck!