(NEW YORK) -- A new study says that pain may be the cause of sudden, unexplained aggression in dogs, Health Day reports.
Spanish researchers studied 12 dogs--11 males and one female--who were brought to a veterinary clinic by their owners because of aggression problems. The dogs were a giant schnauzer, Irish setter, pit bull, Dalmatian, two German shepherds, Neapolitan mastiff, Shih Tzu, bobtail, Catalan sheepdog, chow-chow and a Doberman.
The researchers at the Autonomous University of Barcelona said all of the dogs were diagnosed as having aggression caused by pain, and eight of them had hip dysplasia, a hereditary and degenerative bone disorder that affects the joint connecting the hip and the head of the thigh bone.
The lead researcher of the study said that dogs who had not been aggressive before experiencing pain began to behave aggressively in situations where an attempt is made to control them.
The researchers said the findings of the study suggest that hip dysplasia is a key factor in the risk of large dogs becoming aggressive, according to Health Day.
Copyright 2012 ABC News Radio