How do office desks incorporate ergonomic design?

Very often people ask me what are ergonomic office desks? I mean how could one office desk differ from another so as to be more comfortable when used? Perhaps the primary difference between an ergonomic desk for the office and a conventional office desk is the inclusion of adjustable leg height. Sometimes no matter how much you adjust your chair height you are never lined up correctly to your desk. This is especially true when working with a computer monitor and keyboard. People with exceptionally long or short legs find that simply adjusting chair height does not support proper body position for working on a computer.