When it's medical, not behavioral.
Today we had a 10-something year old dog come in to see us for sudden increase in aggression. He'd had a tough time lately: just moved back to the states, crazy little boys running around, an anxious sister, and a patchy history. He has a lot of baggage and, considering that, he does a great job of taking care of himself.
The family was obviously concerned about the safety of their child. Any self-respecting parent would be. They do a fantastic job of managing their household and preventing problems. They noticed things like in
creased irritability after more exercise, sporadic limping, less activity that before. Things have been changing and they've asked several veterinarians for help. No one listened.
The theory goes that a dog this age is probably about 70-80 years old in human years. I'm not even in my 30's yet and I can tell you I frequently have pain in my foot and ankle. I limp periodically. It's not enough that I'm going to make a big deal out of it; it's just part of life. So now we have an elderly dog who is sporadically lame, has increased aggression, and no one, NO ONE, except the owners seem to think it could have anything to do with arthritis pain?