There are many different types of chair which avoid putting pressure on the coccyx, recommended by coccydynia patients.
Chairs with a short seat
Some chairs avoid pressure by having a shorter seat than normal, so that the coccyx can hang over the back of it. Examples below are a canvas stool, a Directorís chair and a Hag Credo chair.
Here are links to Google searches for folding stools and Director's chairs. Dr Michael Durtnall writes: I help my patients to ensure their employer gets them a Swedish HAG Credo or HO4 chair WITH neckrest... (these chairs are fantastic but expensive)... It can tilt far forward with the feet tucked under the chair & thighs tilted down at 25 degrees & 'back straight' to work on the keyboard... which takes all pressure off the coccyx and gives good working posture with no neck strain!
Chairs with a coccyx cut-out or an open channel
Others have a gap where the coccyx goes. Examples below are a Hara chair, a Putnamís kneeling chair and a coccyx cut-out chair.
Yury writes: The Hara chair really helped - I am able work for 4-5 hours without break and I now have absolutely no problems with normal 9-5 working week (more than 9 hours is still a problem though).
The Putnam's kneeling chair with a cut-out is available from www.sittingwell.co.uk or you could modify an ordinary kneeling chair to create a cut-out. Back specialists say that you shouldn't use one of these for more than an hour at a time, because unlike a normal chair, you can't shift your position much while you're sitting.
Armchair turned backwards
I (Jon) have found that at home, watching TV, reading, etc, kneeling on a padded armchair turned back to front can be very comfortable. You have the padded back of the chair to rest against. You need to find a chair with a back the right height to support you.
Zoe writes: I sit on a gym ball all day at work. I couldn't get through the day without this - sitting on a conventional chair is just too painful. The gym ball allows you to adjust your posture all day. Initially, you can't sit on it all day and have to build up the time you use it for. It's meant to be very good for the general health of your back as your spine is always moving, rather than being static. [The picture is not Zoe]
Helen Buckthorpe writes: I have found a fantastic chair for coccyx problems, that has a tiltable seat, and allows you to sit on it 'back to front'. It has a breast plate, instead of a back, and you lean onto this when sat, to lift the coccyx off the seat. It comes with or without wheels, is height adjustable, and comfy for use all day.
The chair is an 'RH alternative' office seat, and I was provided with this info by 'Sitsmart' a chair shop in Surrey, who were ever so helpful to me, and allowed me to borrow the chairs first to see if I liked them. Having previously tried the RH coccyx- cut out chair and not got on with it, I was most surprised to find the new chair useful. For the first time, I have felt a noticeable difference, as I have been able to stay off my bum totally with the new chair.
The Cleopatra position
If you can find a couch with the right shape, this can be very comfortable. A cushion or bean bag may help to get the right shape and support.
Use two chairs
Rory Greenwell writes: One of the BEST things for me to do is this: if there are more than enough chairs to go around, use two, each leg gets a chair and the gap between them is absolute bliss !!! This works at restaurants and meetings. I discovered this at the YMCA, when we would all sit and talk through our progress with physio. I have done it ever since and it really does work. ...to hell with the embarrassment.
Somewhere else to sit
Jennifer writes: People would ask me why I always took so long in the restroom. Little did they know... I was RESTING! I used to sit on the toilet for a while just to... REST. You know it has that big hole in the center! You can even lean back against the back with no pain what-so-ever. (I just can't lean back in any chair) And, NO pain when getting up! I still do this from time to time. Of course, you can't sit there for too long... your legs will go to sleep.
Bill adds: Jennifer may find it even more comfortable if she used a padded toilet seat. My wife and I are from Australia, and have put them in at every house we've lived in. They are so different, warm in winter, cool in summer, and comfortable.