When dogs, especially senior dogs, lie down in their normal position, the major portion of their weight is supported by their elbows, especially when on hard surfaces. With the passage of sufficient time, and as your dog gets older, the hair covering the elbows disappears as the constant pressure destroys the local hair follicles. In response to this same pressure the skin undergoes hyperkeratinization, a thickening and toughening process, and callouses are formed.

A similar process can take place in the skin covering the hock joints, but this is less frequent. The rate at which these callouses form is directly proportional to the size and weight of your dog. They are rarely seen in Chihuahuas or other toy breeds, regardless of age, but occur with great frequency in German shepherds, Dobermans, Newfoundlands, Great Danes, and most other giant breeds as early as five years of age.

As a rule they cause no problems. If they seem inordinately dry or hard, gently rubbing in a small amount of white petrolatum ointment once or twice a week should keep them soft enough to avoid any difficulties. Once in a while they do get so hard that they start to crack, developing raw fistulas which readily become infected. Your dog will lick at them and compound the problem by irritating the skin. When senior dogs have callouses that reach this stage, they need prompt veterinary attention.