I have terrible knees. Never had had a problem. This works your quads, calves and hamstrings when you push and pull so it can only strengthen your knee joint. Its a pretty stable motion, no twisting or turning or whatever.
The machine itself is just a rower. There is a digital display that does all sorts of recordings. You can play games on it, races, some fishing games, but I just row. I hook it up to a Polar heart monitor which shows up onscreen and keep my HR between 150 and 155. That way I don't burn out or put too little effort in. The resistance is adjustable. It is a full body workout, all cardio.
There is no tv on it. I just youtube some scenery (there's a lotta stuff available) and stream it to my tv, and put some jams on my speakers.
Attached is the readout. You can see as you work out or get a summary at the end. Can even upload data to your phone.