A step-up from walking, if your knees can handle it, is a run-walk where you run but your feet stay very close to the ground. And you move your arms in motion, much like you were cross-country skiing. I used to jog about 3.5 miles every other day and then I ran into toe issues which affected my gait and then led to back issues, and pain. So I went to walking but then tried this new method of walk-run and I have not had a problem since! Since I stay almost as close to the ground as walking, I have not had knee or back issues except when other activities (like roofing) caused them. And it gives me a better workout, minute for minute, than even jogging so I only go about 2 1/4 miles now. The arm motion keeps me balanced and I am not using my toes to push off so much but rather the legs (quads). You can go as slow or fast as you wish with this. I like the fact that I can get a good workout in a little over a half hour.