If poles are what it takes to get someone moving more, then they work.
Whether they "reduce stress on your knees, ankles, hips and back"? I doubt it. First, there's not much stress on your lower body in walking. Walking is low impact, you're not hitting the ground with a lot of force. Second, if your lower body is weak or fragile enough that you can't walk, how likely is it that your upper body is going to be any more sturdy or strong?