Well that is a good question, and luckily there are lots of behaviors you can use to identify signs of pain!! The key word in that sentences is 'behaviours' ....we need to be looking for changes in behaviour and daily habits.
It is a common misconception that dogs will cry out/vocalise (as humans do) when they are in pain....this very rarely the case!! Yes of course when your dog steps on a sharp object or falls down the stairs for example there may well be a vocalisation of pain....but it is very unlikely in the general day to day. Dogs are pack animals and if they show signs of weakness, then of course they would be picked off as the weakest animal in the group, so they are skilled experts in hiding pain!! We must also consider that our furry friends have no idea that there is an alternative state to 'pain mode' , they have no idea that they could pop to the vets for pain mediation, or just resting in bed for a couple of days is what the body needs to reduce inflammation and allow healing. And so we must identify their signals and provide help.
I would say that 7/10 enquiries i get involve the owners telling me that their dogs aren't in any pain "he doesn't cry out, he still chases the ball, runs up the stairs and jumps out of the car.....he isn't in any pain....but he is stiff at night time after resting and he sometimes limps on his walks". Hmmmm that sounds like pain to me!
Firstly lets start with the two types of pain.....
Acute: is sudden and sharp and the response is to protect the body from an immediate danger. E.g. Burning our hand....we rapidly identify the pain, cry out and jump off/ move away from the source of pain....all within a few seconds. Or breaking a bone, the pain is sudden and overwhelming and our body surges in to action to protect itself. Once acute pain goes away (burn or break has healed), you carry on with normal life.
Chronic: a long lasting pain state, it continues even after the injury or illness that caused it has healed or gone away. E.g. Back pain, headache, cancer, arthritis. Pain signals to the brain remain active in the nervous system for weeks, months or years and can be debilitating to other areas of the body such as tense muscles, limited mobility, depression and anxiety (including a fear of doing something that makes the pain worse)
Most pet owners miss signs of pain in their animals, as they don't know what they're looking for....so how can we expect them to know!! Usually by the time an owner has taken their pet to the vets, the signs of pain have become obvious (lameness, lethargy, reluctance to move or use the leg).....by this point we have missed the other subtle signs of pain that came before the severe lameness we are now seeing, perhaps we could have caught this sooner had we known what to look for? Animals often manage in these pain states for months & years before it becomes identifiable with an obvious noticeable problem, such as limping (remember....they don't know there is an alternative, so they just get on with it).
What causes pain?
Just like in humans dogs experience pain for the same reasons such as sprains and strains, breaks, fractures, cuts, bruises, digestive trouble, cancer, pancreatitis, ....the list goes on!
Other less known about causes of pain include Osteoarthritis, Cruciate Ligament Tears, Patella Luxation, Hip & Elbow Dysplasia, Obesity, Spinal Disc Diseases, Bone disorders, Strokes.
So what should I look for?
The following list includes examples of identifiable pain indicators which fall in to different categories:
Posture: Low head & tail carriage, laying unusually, arched spine, leaning/weight shifting
Grooming: Dull coat, change in coat/hair direction or stood up, licking or biting joints & paws, excessive scratching
Activities: Reduced exercise tolerance, slow or difficulty rising/laying down, muscle trembles, circling, restlessness, being too still, hesitancy to perform a task (e.g. walk down a step), sniffing more on walks
Daily behaviours: Decreased appetite, sleeping more, panting for no reason (especially at rest), less willing to play or socialise, snappy or aggressive, growling out of character, increased anxiety levels, vacant expression, groaning, whining
Self-protection: Not fully weight bearing, limping, reluctance to be held/touched, hiding away from social situations, changes in movements (squatting differently, bunny hopping)
But my dog still wants to chase his ball and run around on his walk?
Yep, they will do! Our dogs senses are overwhelmingly enriched when they are outdoors, sniffing, scenting, playing, exploring the world! Dogs get a big endorphin release (happy hormones) when they exercise, especially if that involves toys, balls, socialising etc. This heightened state of excitement overrides some areas of the body...including pain receptors in the brain, temporarily blocking information about pain! Click here to read more about this. So your dog will chase the ball, run around and seem all well and good. You go home and your dog has a rest...when they get up they are stiff, sore and might be a little quieter than usual, perhaps even a bit lame.....this is because the tissues and joints are inflamed and swollen from such high-impact, over-exertive exercise on a problem area of the body. The dog will not put two and two together..... "playing with my ball is what has caused this pain, so I had better stop playing with it". Nope they will continue as normal, until it becomes really painful and long term lasting damage has occurred.
Let's remember...our dogs are unaware there is an alternative state to pain, they will simply get on with it. It is up to us as owners to be diligent and identify the subtle signs of pain before they manifest!!
Top Tip
Take videos and pictures of your dog doing simple activities, every 6 months or so, this gives you a visual way of monitoring changes in your pets and your vets will be pleased to be able to see these too:
a. Walking, Trotting and Running (birds eye view, side views, directly from behind and directly in front)
b. Shaking (if you are quick enough!) c. Eating (looking at their posture) d. Climbing stairs/steps (if this is normal for them) e. Doing a sit to stand movement d. Getting up from laying down
It is really important that when you take videos that it isn't just film of the dogs back....you can't see what they are doing with their legs, which is where a lot of the information comes from. Here is a really useful poster from CAM about how to best take useful videos and pictures of your dog: https://caninearthritis.co.uk/wp-content/uploads/2020/05/Taking-Owner-Collected-Videos-CAM-Guide.pdf
A final word; if you suspect your dog is in pain, please please please seek veterinary advice, don't wait until it gets worse as you could end up allowing your dog to do more permanent damage (that will also cost you more in the future!) and possibly shorten their life span.