Are hiking staffs longer than walking sticks? What about trekking poles and hiking sticks? (I had to get all those keywords in there so you can find this page in the search engines.) Well, whatever you call them, they are supposed to help your knees more than anything. This they do well, especially when you are going downhill.
They also help you keep your balance. You can use them to defend yourself against wild animals as well. I like to use a walking stick to rest my head on from time to time. I also use a walking stick as a monopod for steadying the camera.
Do You Need A Hiking Staff?
What if you don't have knee problems, you are hiking on level ground, and you prefer to sit down for a break? Then, for you, perhaps there is no point to using a walking stick. Actually, I don't use one most of the time. It's just another thing to carry.
Do they save you energy? Well, they take weight off your joints, but logic says you will also expend more energy over-all if you are carrying them. I use a hiking staff at times, because my knees insist, and it is fun to poke at things with it, but it is not always a necessity.