Pain and Exercise in Animal Rehabilitation – what about fear?

Welcome to this week’s knowledge nibble, where we will discuss pain and exercise and have a think about how fear can play a part in animal rehabilitation specifically. 

So first of all as with all the knowledge nibbles, I want to try to provoke a bit of thought.

It is not just about teaching you something new necessarily. It’s about us all questioning ourselves and hopefully, opening our minds to becoming the best practitioners we can be.

So this week, we are going to be talking about pain and exercise. Pain is obviously a huge subject and so we are dialling in on something quite specific here that perhaps we might not have thought about so much previously or not currently thinking about that much within our practice. I just wanted to cover a different aspect and see if we can start thinking about something a bit different.

First of all, I just want to look at the traditional approach and what we tend to think about with pain when we are using rehab for animals. We tend to think pain equals tissue damage and we think about tissue damage being a noxious stimulus. That might be an injury or wound or a repetitive injury (basically something there that is causing this tissue damage). Firstly, a noxious stimuli can cause tissue damage and inflammation. Nociceptors will then carry that information towards the central nervous system. The brain will perceive it as pain or it is interpreted as pain. That is how we normally think about the pain pathway and how it relates to rehabilitation. 

Following this, the treatment would then tend to be a standard approach to rehabilitation or treatment would involve removing the noxious stimuli first. As mentioned previously, if that was an injury (for example, it was a wound/ actual traumatic injury), that has healed and is no longer an open wound. In that case, the noxious stimuli has been removed and we should be moving on to healing.

It may be something such as hoof balance in horses and it may be that we have rebalanced the horses hoof. In dogs, it may be something such as repetitive strain injury from jumping out of the car every day. The first step would be to take away the element that is causing the injury in the first place. There are occasions where we cannot carry this out when it is related to internal factors such as conformation, but that would be the first type of step in the plan. We then need to think about the next steps. The promotion of healing will follow and this will sometimes include rest. If it is not full rest, then it may possibly be rest from exercise or rest from extreme exercise. It might also include NSAIDS or corticosteroids (something to reduce the inflammation and help with pain control – pharmaceuticals).

After this, we would be moving on to the rehabilitation aspect. Within the rehabilitation aspects, we will be thinking about where we are allowing the injury to heal, or we will be promoting tissue healing. Tissue healing can be carried out by the use of electric physical agents or manual techniques. It is this point in time where we want to promote that tissue healing and the time frame is very important. 

We need to now think about increasing strength and function. The way we normally think about pain and exercise specifically is that we want to address dysfunctional biomechanics. If the biomechanics are not optimal and there is muscle imbalance and problems with function, muscle firing, and motor control, etc. The consequences of this will be more stress and strains on the joints, tendons and ligaments. Trying to address that dysfunctional biomechanics is a very sensible approach. 

Sometimes it is all great and it all works. But what do you do when it doesn’t work? What actions do you take when there is pain in the absence of tissue damage? The pain comes on either in the absence of tissue damage (no initial injury that has been obvious or there has not been a problem diagnosed) or it is after tissue damage following healing when everything should be fine and looks fine. If this is the case, why do we still have a problem? 

You may have just thought about why there might be pain in the absence of tissue damage.

My reasoning or answer for this is that it is important for us to understand that we can have a pathological pain state so we can have a dysfunction of pain. Pain is not always and does not always make sense. It is not always that we damage the tissue and therefore it hurts. We heal the tissue and therefore it will not hurt anymore. Unfortunately, as much as I would like that to be the case, it is not as simple as that. We can get into a dysfunction of pain and a pathological pain state and that is what we are going to go through. Have a little think about the aspect of a pathological pain state, the emotional and the fear responses. This is what I am going to discuss.

Central sensitisation and persistent or chronic pain (‘persistent’ seems to be the more modern term for ‘chronic pain’). This is in the central nervous system which means this is a central nervous system issue and not a peripheral issue. This is not pain in the foot that has been persistent. It is not tissue damage or related to inflammation. It is a persistent pain that is being recorded within the central nervous system. You can think of it like an overreaction. It is very over-reactive. Everything in the body is firing off and initiating pain responses when there is really nothing to be painful about.

I am going to briefly discuss a very complex subject and I will try and keep it simple. During an overreaction there will be hyperalgesia, which is an increased pain response to normal, painful stimuli. For example, a horse having an injection. If a horse has a vaccination administered into their neck, they may react very dramatically about a little pinprick when they really should hardly feel it at all. It should be painful because the skin is being punctured and it is a noxious stimuli, but it should not be massively painful to create a massive dramatic response. It may be hyperalgesia where there is an over dramatic response to, what would be a normal, painful stimuli, but it would normally be quite tolerable.

Of course with animals, it is not this simple and a lot of this research comes from human literature. When it comes to animals, as we know, it is not that simple because it is very difficult to interpret what they are thinking most of the time. We cannot simply say to an animal ‘did that really hurt you?’, ‘did that actually hurt you or are you just frightened?’, ‘did it give you a shock?’, or ‘were you surprised about it?’ etc. It is very difficult because we do not have that level of communication with animals which is why we need to be very sensitive. 

Allodynia is a painful response to a stimulus that is not normally painful. For example, stroking an animal. Usually you should be able to stroke an animal without them reacting as if they are in pain. A very soft stroke shouldn’t be a problem, but they can have a pain reaction to it. Again, that is an overreaction from the central nervous system and the pain response also referred to as heightened nociception. 

I would like you to start thinking a little bit differently and the hammer is representing repetitive strain and tissue damage. Let’s try to come away from always thinking that pain is the tissue damage and pain is the inflammation. If there is no inflammation, then there is no pain. If there is no pain, then there is no inflammation. Obviously that is when we need to think about pain control such as NSAIDs and steroids that work on the inflammatory mediators and the inflammatory processes. If there is no inflammation, tissue damage and inflammation causing the pain, then they are not going to work. We can sometimes administer NSAIDs or corticosteroids, or similar medication and then not get a good response. And that is because the pain is not an inflammatory pain as such, so they will not work on those pathways. 

So what I want to come away from is always thinking about tissue damage and inflammation and pain, and try to think about the animal as a whole system. We always discuss and refer to biomechanics and how biomechanics is a very important part of it, but it is not really mechanics so we don’t change parts. We do not take pieces and put them back together (I wish it was that simple!). We could just shorten it, tighten something up on one side and then loosen something on the other and then be done with it, but it is a living being so we should be thinking more about the whole ecosystem. The whole system refers to the neurological system, the musculoskeletal system, the digestive system, the blood vascular system, the respiratory system – everything is intertwined. You cannot just separate them so try and think about the whole ecosystem of the animal and specifically (during this topic), the neurological system.

How does the CNS adapt in pain dysfunction? These are the unusual responses (this is not what you class as normal). There are physiological responses. It is important to note that there are structural changes and these are very complex. You can find out information about it by conducting research. They are very complex and will tell you what actually happens structurally within the central nervous system. There is an immune response to briefly refer to here just so that you understand there are some physiological responses. There is an immune response which can increase inflammatory, mediators, cytokines, etc. The immune response is actually quite a big part and plays an important role. It has a connection to the amygdala and the fear, but we will try to keep it simple and think about the increase in inflammatory mediators. 

There can be a change in cell behaviour and our receptors. What might have been a proprioceptor may have changed into a nociceptor and vice versa. They communicate in the dorsal root ganglion and they can also change their behaviour. This can then lead to an increased responsiveness of nociceptors. Nociceptors can become increasingly active and increasingly sensitive. Also, other cells can act as nociceptors and glial cells can take on that role. This overreaction has taken place because there are more of them which then leads to a more amplified pain response (or ‘ramping up’). It can get progressively worse as time goes on in patients with chronic pain or persistent pain. 

This is the main thing taking place, but then there are also psychological responses. I believe this is where we can really have an influence with the use of exercise and treatments. It is important that we look at both of these and try to think a little bit outside of the box about how we may be able to use these or influence these to make a change of our perception of pain. This then leads on to the perception of pain in animals. So first of all, it is important to establish that pain in the brain (a little bit of debate in the literature and scientific research about this). But pain is not in a joint or in muscle or in a tendon.  Perhaps the cause of the pain might be there, but it is not pain until it is interpreted as such in the brain.

Pain is a very personal experience. If I was to hammer a nail through the hand of several people (which I wouldn’t do!) and then asked those people to give me a score of one to ten in relation to their pain, I may receive a range of different scores and responses. One person might say four (they are obviously quite tough!) and another might say 8. It is a completely personal experience and it is subjective. We are not really able to reliably interpret what one person might feel against another. We may be able to interpret what one person may say is an eight and my pain has decreased to a four. But the point I am making is that trying to measure that against other people is just impossible. This is the same for animals.

Some animals will have a heightened pain response or perceive a particular stimulus as extremely painful, and another animal may not even notice. We will find that with our therapies that we carry out and any of you that are nurses will know that when you handle these animals and when you work with them, you will notice that some are very dramatic and some are not. It could be that their anxiety and their fear plays a part, but it could be that they have a very different perception of what pain is and how painful things are.

We also have communication issues and as I have mentioned previously, you cannot ask an animal ‘Are you in pain or are you scared?’. Other questions you cannot ask are ‘Why did you react like that?’ and ‘Are you in pain or are you scared?’.  I find myself as a therapist very often gently repeating something and trying to distract them to see if that really does hurt or were they just not expecting it. You also cannot ask ‘how bad is the pain?’, ‘is it always there or is it only when you move?’ or ‘what type of pain is it?’. 

We cannot differentiate between different types of pain. Is it a throbbing pain? Is it an acute pain? Is it a stabbing pain? We cannot communicate in that way with animals. We can observe their behaviours (and you should do this as well), and you should study pain behaviours and you should know what these are. However, we cannot interpret what is behind that behaviour or behind that face or behind that response. We cannot state how bad it is from one animal to another. We also cannot articulate to an animal that is transient (which I think can be quite upsetting). For example, if you have a really bad toothache then you can say to yourself ‘I know I have antibiotics and I know that by tomorrow it is going to start to feel better. An animal does not have that judgement. So it really hurts right now and as far as they are concerned, that is it and it is going to hurt like that forever. We can’t articulate that to animals, which I think is a bit sad really.

Moving on to physiological factors. So this is where I really want to go into more depth. Emotional states can modulate the individual’s pain experience. That is a very important factor in animals. It has been shown in human studies and it is quite well known that emotional states such as anxiety, depression, and catastrophizing can increase your perception of pain and your individual perception of pain. If you are in a particularly anxious state, then everything might hurt more. If you are very depressed and everything might hurt more, or sometimes it does not hurt at all and you cannot feel anything. 

Catastrophizing is something that is quite interesting in animals because (as mentioned previously) they do not have that sort of forward projection. They do not have the same sort of analytical brain that we do. Catastrophizing can lead to a real ramp up of pain. For example, if I have been diagnosed with osteoarthritis and I have just gone home and I think ‘Oh my Goodness! It’s going to get worse’. And then I may make myself really worried and stressed about it and this may lead to it becoming a lot more painful. 

I do believe that animals worry. So if we get ready to go away on holiday and we are packing our bags, or even getting them out in the loft, our dog will know about 24 hours to 48 hours before we go away that we are going away and she will worry about it. She will sometimes not eat or she gets upset and she completely changes her behaviour. So I believe there is pattern recognition and they can recognize patterns and therefore perhaps they get really worried. If an animal becomes really worried every time somebody goes into the loft, that is catastrophizing.

There are some of these elements like self-efficacy and other similar elements that I believe probably are not related to animals. I believe catastrophizing is something that we should keep an open mind about, but generally we know that animals can be very fearful. We do not have that communication where we can say to them ‘It’s okay. I know this hurts, but it’s fine. Don’t worry about it. It’s going to be fine tomorrow’. The fear can have a massive influence on how they are feeling pain. I just want you to reflect for a moment and the question I would like you to ask yourself is how much of what we see as persistent pain is actually caused by fear and survival? In animals, if we have a persistent pain problem, is it actually associated with fear? Just have a little think about that before we move on. 

So how can we use exercise in cases of persistent pain? There is a physiological response. Again, it is a very complex process and there is a phenomenon which is exercise induced analgesia. This is caused by stimulation of the endogenous opioid system and reduces pain sensitivity. It is like the natural endorphins or natural opioid system and it has been shown in many studies that there is this analgesic effect of exercise. If you have chronic pain, it can get worse at first, but if you can get through that pain to the other side and carry out regular exercise, it can actually help reduce pain sensitivity. That is physiological again and is a structural change. Thinking about the psychological aspect, what we want to do and what we want to think about is the reconceptualisation of the pain related fear.

We believe the animals we have worked with are fixed. They have still got a movement asymmetry, which will be very often put down to proprioception deficit, which is very true too. This can all be a part of the same pathways. Again, we are an ecosystem and we are trying to separate something out, but just try and think about it individually. There can be a fear of pain, a memory of pain and fear of movement. In humans, there is a known phobia called kinesiophobia  (a fear or a phobia of movement). People just will not move because they are so frightened that it is going to hurt. If you think about it, animals are like that.

They may have a memory of what the pain is. For example, every time the saddle goes on, it hurts them. Even though it can be altered to fit them better and it is more comfortable for them, it will still hurt them. They did not know the difference. Every time I moved up a hill, it hurt them and they are fearful of that pain. They therefore do not change their movement because they are in fear.

Anxiety is a very important one. So if the animal is in fear when they come to you, everything is going to be emphasised. If we have an anxious patient, at some level they are probably anxious unless they are really chilled out and laid back. But if they are in pain, then they are probably anxious to some degree. The fear of you being there, the fear of something different and a fear of you being near and going directly to the point where they do not want you to touch them can really heighten this experience. For those of you that work in a vet practice, animals coming into the vet practices is ample enough for them to experience an anxious state. They will remember being there before and it hurts so some of them can be very anxious about visiting the practice.

It is something we just really want to think about. 

We want to try and think about how we can work on those animals so we can reduce their anxiety and the pain that they feel when we are working with them. We want them to become more confident to push through that and come to the other side. Working with humans, the way they will deal with this is if there is a fear of movement and a fear of going into any kind of range of movement or an understanding, a human will think ‘well, if I do that, I’m going to damage my tissue again’. They will say to a human ‘this is going to hurt, but it’s not going to damage your tissue anymore and it’s going to make you better. If you do these exercises and you can get to the other side of it’. You can talk them through that. We do not have that. So how can we get to the other side of this without inducing pain or too much pain? Discomfort is acceptable if we are doing it for a good reason. We have got to calm them when they are in discomfort otherwise we raise their anxiety and that will then raise their pain level. It is very important that we have a good connection with this animal and get them to trust us. This is why it takes three or four times as long to achieve something with an animal as it does with a human. 

With depression and catastrophizing, we can put these two together. This is more related to lifestyle. Enrichment and distraction are very important. Horses that are kept in a box and are depressed and segregated from their friends. Animals that are at home and have got chronic pain. They do not walk out with their friends or go out to play with their friends. They can go out and just sit out and watch everybody. Horses can be led out of the stable and be held so they can see their friends. It is enrichment and trying to raise their spirits and it will help them with their pain. It will hopefully help them be able to move through this painful period and try to reduce this neurological overreaction.

Have a think about those aspects within your practice and also what you have seen in the past. Have a think about the patients you have seen and think about whether you can relate this. Reflect on the patients you have previously seen in your practice and also moving forward.

So your action this week is to debate the following questions with one of your peers. Connect with somebody on Facebook or speak to somebody that you have trained with. We all have somebody else that we know that is a therapist. Prompt them and poke them and discuss this with them because when we are in debate, that is when the learning takes place. When we are having discussions, just because we think we know something does not mean it is right, so we have to debate. 

So find a friend and if you can answer these questions or debate these questions with a friend in cases of central sensitisation, how can we use exercise to calm the nervous system and address fear related pain in our patients? How are we going to actually do that? We know it will help, but how can we do that? What is the difference between how we treat an animal who is in pain through tissue damage and a patient who has a heightened perception of pain in the absence of tissue damage? We are focusing on it hurting because it is broken or it hurts because I think it hurts. 

Finally, I would like to say it doesn’t really matter. It matters as to how we address it, but it does not really matter if it hurts because there is tissue damage or it hurts because I think it hurts. If it is still a five on the pain scale to me, to an animal personally in their experience, a five (whether it is tissue damage or whether it is just pain) perception is still a five and it is still pain and we still need to address.