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PLEASE NOTE: While I consulted a veterinarian and veterinary sources when writing this article, it is not intended to replace an examination or treatment by a veterinarian. 

Most behavior problems like anxiety or aggression are caused by stress, either due to a lack of socialization, learning history - including trauma, or genetics (from parents, grandparents, and beyond). When gathering a dog's behavior history, at least one of these causes can usually be found.

But when a dog's behavior changes suddenly or doesn't fit the usual patterns, it could be a sign of a medical problem that is causing pain or discomfort. If you see any of these or any other recent behavior changes in your dog, contact your dog's veterinarian before starting a training program. 

New or Unusual Behaviors

Either the behavior started or drastically escalated over a short time period and does not have an obvious cause, such as a traumatic or painful event. 

Sudden onset of fear or aggression. Hiding, trembling, running away, snarling, growling, snapping, or biting in situations that were not a problem in the past. 

Conflict with other household pets. New aggression toward or avoidance of pets with whom they previously had a good relationship.

Whining. Some dogs are definitely whiners, but new and repeated whining could be a sign of pain.

Noise intolerance. This is one I didn't know until recently! Fear of loud noises, especially in older dogs.

Panting. Panting repeatedly and heavily when not hot or active. Note: Heavy panting can also be a sign of emotional stress.

Repeatedly shaking head. Shaking just their head and not their full body (like they do when wet). May also include tilting head to one side and/or ear held in different position than the other.

Repeatedly licking the same spot. Repeatedly licking one area of their body, as opposed to normal grooming.

"Fly snapping" at the same part of the body. Dog whips head toward part of the body and snaps at the air when no "fly" is present.

Pressing head against wall or other surface. Head pressing can be the sign of a serious medical condition.

Spinning, light chasing, or other repetitive behavior. Stereotypic (frequent, repetitive, and seems to have no purpose) behavior usually requires veterinary intervention.

Change in Normal Routines

Some behavior patterns change gradually as dogs mature, but sudden changes could be a sign of something else.

Energy Level and Sleep Patterns. Includes restlessness during normal sleep times or reduced energy and sleeping more than normal.  

Appetite. Refusing meals or other food that was enjoyed previously or change in eating habits (slower, faster, less or more frequency, etc). 

Housetraining. Sudden regression and repeated accidents in dog that was reliably housetrained for a long time.

Change in or avoidance of normal activities.

If your dog usually looks forward to walks or plays ball as long as you will, or you see a change in their sociability, they may not be feeling 100%.

Walks. Avoidance being leashed or harnessed, refusal to leave the house, or turning/pulling back toward the house. Also, frequently lying down on walks and refusing to move forward.

Play. A change in interest for a favorite toy or game, such as a ball-crazy dog walking away after one or two throws.

Self-isolation. Choosing to hide in small spaces or hang out in other rooms at times they used to enjoy being with you

Change in Training Responses

If your dog has always responded quickly and reliably to trained cues and you see these changes, don't write it off to being stubborn or defiant.

Slower response. Taking more time to respond to a cue that requires a position or action that could be causing pain, such as sit or down. 

Refusal. Not responding to well-trained cues and/or offering different behaviors in response, such as lying down when asked to sit.

Disengaging from training sessions. May start training session with enthusiasm, then stops engaging or never engages.

Longer recovery from stress. Example: a dog that reacts to other dogs on walks normally recovers after passing the dog, then suddenly remains agitated long after the other dog is out of sight.

Unusual Posture or Movement

While there are variations depending on size and breed, when a dog is hurting, the signs can be subtle and include:   

Skipping step and "bunny hop".  The dog intermittently skips a step on one leg while walking and/or hops on both back legs simultaneously when running. This video has some good examples.

Skipping from walk to run - avoids trotting. See the gait video below for examples of the trot.

This short video shows how dogs move and place their feet at different speeds. If you routinely notice their gait does not follow these patterns, ask your veterinarian.

Only running up/down stairs or other unusual gait on stairs. See the skipping step and bunny hop video, above, for examples. 

Hunched posture. Dog's spine is arched instead of straight. 

Low head. When walking, dog consistently holds head below spine. 

Difficulty getting up or down. Dog is slow or hesitates to sit or lie down, or needs to work up momentum to get up or jump up in raised areas.


Dogs can’t rationalize their pain. They aren’t able to wake up with a sore leg and connect it to the epic collision they had at the dog park yesterday. They can only make associations between the pain and what is happening right now.

Those associations - positive or negative, pleasant or unpleasant, safe or unsafe - influence their future behavior. 


A client’s dog bounced toward me during a fun training session. As he moved to take food from my hand, he yelped and wouldn’t put weight on his leg. The client went home and we rescheduled. The next session, the dog resumed happily bouncing…until I offered food. He backed up and wouldn’t come closer. An association had been made between pain and my extended hand. Fortunately, we were able to overcome it quickly.


These associations can be made to people, places, and other pets, even when there was a long and pleasant association in the past. The longer a dog experiences pain or discomfort, the more negative associations can form and strengthen over time, which could have a significant impact on their behavior. 

Don't Delay. Schedule a Veterinary Appointment.

If you hire a trainer for a problem caused by a medical condition, you won't get good results. And if you delay a vet exam, your dog could have a medical condition that will only get more expensive if left untreated.

If there isn't a clear finding after the exam, but pain is still suspected by you and/or the veterinarian, ask if they are willing to test a short trial of pain medication to see if the behavior improves. If so, that may give them important information to continue treatment.

Finally, don't attempt to diagnose or treat suspected pain on your own. Over-the-counter and natural remedies (including CBD) can delay relief from pain and necessary medical treatment, causing your dog to suffer longer than needed. 

Recommended Veterinarian in Seattle/Tacoma: 

Dr. Micaela Young at Happy Lead Vet  

Additional Reading

Pain's Effect on Behavior

Dog with behavior problem caused by illness

A thyroid condition caused major behavior changes in this dog, which were resolved with an inexpensive medication.

Schedule a Free Consultation

Schedule a free phone consultation. Let's talk about what you're seeing.
If I suspect a medical cause, I'll recommend you talk to a veterinarian
before scheduling any training sessions.

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