If you are on short term or long term disability leave, the employer is under no obligation to promote you. For instance, if you were a ‘Junior Manager’ at the time of your leave, you cannot demand the same promotion your peers may have got.
If you are unable to resume your previous responsibilities due to your disability despite accommodations, your employer can reassign you to a more appropriate role. This too does not have to be a ‘promotion’, and can be in an equivalent or lower position.