I have 2 clients, age 60, over weight, total knee replacement one year ago. what to do next?

both have been using weight machines without incident but would like to change up their routine but every time I try to incorporate a new free weigh lower body exercise they don’t want to do it for fear it will hurt their knees. They are doing the leg press, leg curl, leg extension machines now and have no problems. Are there lower body free weight exercises that do not include, squats, lunges, steps???