Kneeling chairs -- what do I need to know?

Hi all, I'm considering the purchase of a kneeling chair for sitting in my office several hours per day and I wonder if any Permies know things I should know before I spend any money.

First, this is the kind of thing I'm talking about: https://en.wikipedia.org/wiki/Kneeling_chair

My roommate Erik, had one in 1991 and I sat in it a fair amount. I found it comfortable. But I haven't spent any real time in one since then and my back and posture have degraded over the intervening decades. I currently switch between a folding chair, the largest yoga ball, a rocking stool, and standing.

Do you sit in one? What do you think about it? What factors should I be considering when deciding what to buy?

I see that some are on rockers and others on wheels, and others just sit on the ground. Do I care about that? Some have backrests, but most don't. Some seem to have adjustable height/angle, but most don't. How are those features? What else do I care about?

One of my friends was into them for years. She said to avoid the ones with a seat back (for core muscle health reasons.) She preferred the rockers, but they don't mix well with pets who are stupid with their tail. If you're a bigger person, check the weight limits on them.

I don't like the rockers, personal opinion. I DO like the wheels, BUT that chair takes up a LOT of floor space compared to my desk chair on wheels. Even if you are not using it.

I have one like the 3rd one from the left in the top row, and I like it a lot because I can adjust the height of the chair and knees, although if I could design exactly what I wanted, they would adjust separately, I made a really solid seat cushion about 5 inches high to get my angles exactly right for me.

I would recommend go to someplace and try a few to see what your body likes at this point. You are used to using no back at least sometimes, but where your center of gravity is vs the chair might be a factor to think on. If your weight and position push hard onto your knees, you'll hurt them. If you have to lean forward to reach your computer on the desk, it's going to injure your back more. So you want your center of gravity to feel balanced when your knees are not taking any strain, and you are sitting up straight and can reach the desk properly.

One more thing, they do flip over backwards easier than you expect, I was surprised with the long wheelbase length just how easy it went over. Consider if you tend to get hurt if you fall badly vs what you'd hit if you did flip, what's behind you at your desk? Anything you care to hit? And if you have to adjust the seat and knees high, that shortens the wheelbase and makes it easier to flip.  Worth considering.

In general I love mine, helps my back etc, and I used it for years. In specific, I don't have the space for it right now, and I got hurt badly when I flipped it and landed on painful things.

i also had one in college in my house and we all fought over it. i would love another one.
i'd also say, avoid the backs and the rockers-- as mentioned they do fall over. I wanted stability. I second pretty much everything Pearl said above.

I used one similar to the third from left, top row, with a height adjustment, in my office for awhile.  It was OK but clumsy to get in and out.

I have never heard of such a thing--maybe I should get one myself. I wonder if it is better to stand at a desk if possible or use a chair like this? I read on the exercise bike but I couldn't teach that way, so I am looking for something useful.

I have never seen or used a kneeling chair. I kneel enough without a chair though, sometimes using an ordinary firm cushion but oftentimes just on a floor, carpet or earth.

Some people put a cushion or blanket under them, and then use another cushion between their heels and bottom.

There are also low "meditation benches" that some people use as well, which would probably be quite easy to make. All these options are with the lower legs relatively flat to the floor so I'm not sure how much use they will be in this circumstance but I thought I would mention them anyway.