Most people still sit at desks that are not height adjustable and this can be a problem. Although the majority of people are now sitting in adjustable chairs this just means the chair will fit better, office tasks however are done usually at a desk.
It is becoming increasing more common to see upgrades to varying-height desks to accommodate the differences in shapes and sizes of individuals. If the desk height is fixed then the chair adjustment needs to accommodate the desk rather than the individual. The vast majority of problems come from when the desk is too high relative to the chair. This usually again causes compensations of posture and the risk of muscle tension, fatigue or pain.
In this situation it is best to adjust the chair so it is raised, and have a footstool to accommodate for height difference.