Fear induced aggression or pain induced aggression is something that may affect all older dogs at some stage.  This is simply because many dog owners don't realize their aging dog is very sensitive to feelings of pain, surprises, and aggressiveness - even from innocent play.

You'll need to pay attention to changes in your pets' manner or personality to pick up when things are becoming difficult for him. If you do, you won't be surprised by a full-blown fear of things that never used to bother him. For example, he may react to jumping up into the car to go for a ride. If your dog can't see where he's jumping, or if it hurts him to jump, it can lead to fear-induced aggression. He may strike out against you, seemingly for holding the car door open.

Aging dogs get into biting for similar reasons if they're experiencing discomfort. Pain-induced biting can be a result of forcing them to do things that they're no longer able to do. And this in turn can lead to fear-induced biting if, in their eyes, you're about to force them to do the painful activity. If it's jumping into the car, they become afraid of your reaching for the car door handle and nip the hand you're using to hold them because of the pain they know is coming. Creaky old hips aren't meant to propel a slightly overweight frame onto the seat of an SUV, even with the help of a push from the rear. And nips like this are your dog's way of telling you there is a problem, especially when you haven't picked up their signals before.

Sometimes children or grandchildren forget that the dog is not as young as she used to be. The smaller the children, the more they will need reminding  - for their own safety, as well as for the comfort of the dog. Many dogs are likely to become aggressive if they are hurt while being picked up the wrong way by an unsuspecting child. Sometimes it's necessary to set new rules in the household for the kids who come over to visit: "Frodo is not feeling well today. Please let him be by himself in the corner," or "Frodo is old, and he's feeling a little grumpy today. Maybe tomorrow he'll feel a little bit better, but let's leave him by himself today."

Similarly, if one of your younger puppies or dogs starts to get into a play that's too intense for your older dog, redirect his activity and play towards yourself, or toward self-play. It's up to you to intervene on behalf of your geriatric pet. If it doesn't look like she can take it any longer, she'll thank you for sure, and your relationship will grow because of it.