My mom has one and she really likes it. She has a treadmill that is about 8 years old that she wore out and decided to go with the tread climber for something different. My mom had 3 knee replacement surguries ( the 1st one she was fitted with the wrong size joint) and it been about 16 months since her last surgury. As far as knee comfort you get a good comfortable work out. I tried it and you can feel the burn as if you had a traditional treadmill on a deep incline which is not the best thing you are prone to knee aches. I'm actually considering purchasing one my self. Hope this helps
