Many dogs are susceptible to pressure sores if they spend too much time lying on the ground, or on a hard floor.  Pressure sores are normally seen as a callus on joints that have a thin layer of skin over them.  This area can occasionally become infected, and the owner needs to keep aware of it, other than that, the callus is simply a cosmetic problem.
     To prevent calluses, the dog should have a well padded bed that is kept where ever the dog has a tendancy to lie down to sleep, or relax with the family.  There is no particular type, it simply needs to be long enough for the dog to stretch out on.  As to the esthestics of the bed (e.g., color, filling, thickness) that is up to whoever is paying the bill.