I have arthritis and an inflammatory disease, and the chair I use is very important.  The mid-back support by the flexible mesh is not only comfortable, but I also use it to massage my back.  My legs have neuropathy with a great deal of pain, and the very comfortable seat cushion helps relive my leg pain.  I highly recommend this chair to everyone, especially anyone with medical issues.  
The pushup arm rests comfortably help stow the chair close to the desk.