bald areas on dogs elbows

Question
our 2 year old border collie mix has a circular, bald, dime size area on the outer edge (not bend)of each  elbow. it is not red or calloused. It is not the normal pressure area seen where dogs constantly lay on the area.  there are no other bald areas, his hair is shiny.  He sleeps on a dog bed at night, but prefers the cold floor during the day.  He is not kept in a kennel.  He is an inside dog. the area is not scaly.  he has had the areas for a year.  they have not increased in size.  the vet thought it was a pressure area a year ago.  he does not lick area, but does not like me to run my finger over area (does not flinch, but pulls leg away).  any thoughts?  

Answer
I agree that this is most likely from pressure.  If you doubt this, then you can have a biopsy done to see if there is a disease of the skin that may be present.  In the elbow area, it is very common for callus tissue to develop.  Early on, these areas are red and devoid of hair.