Cause
A genetic cause is thought to play a major role, as the disease is highly prevalent in some lines of German shepherds. Underlying elbow incongruity, or elbow dysplasia, also may be an important factor. Damage to the distal growth plate of the ulna may result in a shortened ulna, putting excessive force on the anconeal process and preventing it from fusing to the ulna. Other factors include problems with the dog's nutrition, such as obesity or high calorie diets that are intended to promote rapid growth, hormonal effects, and chronic trauma.