By Dr. Kayte Armstrong DVM, M.OMSc, and Lee Jarvis, M.OMSc. Editing and proofreading by Christina Burris.
Dr. Kayte Armstrong is a Doctor of Veterinary Medicine and a graduate of the Canadian Academy of Osteopathy (CAO). Kayte earned her Doctor of Veterinary Medicine (DVM) in 1999 and graduated from the CAO in 2018. Kayte began teaching at the CAO as a junior instructor in her final semester and became a full instructor upon graduation. Kayte has instructed manual applications, supervised the student clinic, taught Osteopathic Theory, and is currently the Anatomy and Palpation teacher. In 2019, Kayte launched the Graduate Diploma in Animal Osteopathy program at the CAO, which she continues to lead. In addition to teaching at the CAO, she also runs a practice for both humans and animals in Nova Scotia.
I spoke with Dr. Armstrong in February of 2024, covering various topics related to Osteopathy in both humans and animals. Kayte was bursting with her usual overwhelming enthusiasm for the subjects she enjoys. This enthusiasm is always fun to be around and makes our conversations effortless. One fascinating subject that quickly arose during our conversation was the subject of comparative anatomy. Kayte explained that her previous and continued study of animal anatomy and Osteopathy is consistently one of the best ways of informing her human anatomy and Osteopathy. Further to this, Kayte stated that even a cursory or initial exploration into comparative animal anatomy is beneficial to the Osteopathic practitioner who works only with humans. As such, leveraging this benefit will be the goal of this article (hopefully both for the reader and the author).
It’s always worth remembering that the origins of Osteopathy, and its discovery by Andrew Taylor Still, were heavily influenced by the study of animals. Like many of his contemporaries, Dr. Still grew up and worked on a farm, which was necessary to provide food for one’s family. His life on the farm afforded Dr. Still many opportunities to make observations about animals, which are relevant today. Dr. Still studied these animals through both behavioural observation and dissection. For reference, consider this statement from the Autobiography of A.T. Still (page 326):
“When a mule has worked all day, and the muscles of his spine are pulled out like a shoestring, what does he do? He finds a good place to roll, kicks up his heels, kicks another mule or two, and has gone through his Osteopath manipulation. He shows a little sense. An old hen when she gets what you call microbes in her feathers, does what? She gets out her microscope and looks through, and concludes they are microbes; then she hunts up a dust-heap, and leaves them there. Watch the hog. He knows more than his master; when he gets the fever he goes into the mud and stays there until the fever leaves.”
For clarification, in this case, we believe Dr. Still to be referring to the hen’s beak as the microscope. While we can appreciate this anecdote, I hope that it goes without saying that, unlike the mule, we should not kick animals (or people) in hopes of alleviating somatic dysfunction(s).
Today, most of us do not have opportunities to study animals in the same ways as Dr. Still. Most of us are perusing this article from the comfort of our laptop or phone – perhaps even having this article read aloud using text-to-speech (a good choice, by the way). Nonetheless, our technology allows us to view animals from a distance, instantaneously, and in decent detail. Viewing animal anatomy through a book or phone may lack the palpatory effect gained by being with a live animal, but a practiced mind can make up for the lack of palpatory information.
As we continued our conversation, Kayte brought up the idea that Osteopathy is integrated into all aspects of life. We often talk about how our Osteopathic assessment informs us of what is going on in the body, how our Osteopathic treatment restores the capacity for the body to manage/heal itself, and how the body is a part of nature. Given these concepts, it is only logical for us to aim to see Osteopathy in everything we observe. Kayte then reiterated this more comedically: “Everyone’s doing it! The Osteopathic Lesion that is.”
Following this train of thought, if all animals are made of similar cell types, tissues, organs, and systems, they can and will become dysfunctional in similar ways. Animals respond to Osteopathic treatment just as humans do. In fact, according to Kayte, most animals respond to treatment much better than humans do. This is a slight aside from the article’s main topic but is far too interesting to leave out. Based on Kayte’s experience treating animals and humans, she has created a scale showing how they “stack up” concerning treatment responsiveness:
Horses and Cats:
At the very top of the list, both horses and cats clearly seem to have the fastest response to treatment. “Response” in this case means the speed at which the treatment takes effect and/or the number of treatments needed to achieve the desired beneficial effect on the animal.
Horses and cats, more than any other animals, appear to want treatment and allow the treatment to occur without resistance. Kayte explained that, due to cats’ and horses’ capacity for high-speed ambulation on a small foot, they need very high amounts of sensory reception and proprioceptive capacity to balance their comparatively much larger upper body on a small foot. She believes that this is the reason why these animals to respond so well and adapt so quickly to an Osteopathic treatment. Logically, it is not a stretch that an animal that is constantly and rapidly responsive to touch should be so responsive to a therapy that utilizes touch.
Dogs:
Dogs are a close third on the treatment responsiveness scale. Dogs are certainly responsive (and very agreeable) to treatment and are quick to improve in both movement and behaviour. Their relative order on the list is well-earned, though it is still noticeably less than cats or horses. We must acknowledge that the dogs that live in our homes today are a far cry from the dogs of the past. In the thousands of years since dogs have been domesticated, they have been selectively bred for their size, appearance, and personality traits. This has increased in recent years with smaller, non-working breeds. Conversely, although cats and horses have also been domesticated to some degree, they are doing relatively the same job and intensity of work as their ancestors. While there are certainly some cats and horses bred specifically for their size and appearance, just as some dogs are still bred for their hard physical work, so we can’t consider this list to be absolute for every single cat, horse, and dog.
It is worth noting that the most achievable and observable evidence of Osteopathy’s effectiveness likely lies in the treatment of animals common to our homes. Not only do animals have far less “red tape” around their academic study as compared to humans, but it is much easier to control for a placebo effect. Animals cannot be convinced through language that some known ineffective movement or medication will benefit them, and so the effects are not obscured by expectation. Large groups of animals are available for a more than appropriate sample size and their schedules are, arguably, open and available. Hopefully, in the future, we will see more resources for Osteopathic studies framed around the improvement of the health of an animal simply for that purpose and solely not to justify the exploration of a human study.
Pigs, Ducks, and Geese:
Continuing down the list, Kayte has indeed worked with pigs, ducks, and geese in her professional experience, but their inclusion on the list is mainly to emphasize the following statement: Humans are at the lowest level of responsiveness of all the animals that she has observed. This is not an insult to humans; it is simply an observation of tissue changes over time. The observed tissue and relative nervous irritability in humans change that much slower and take many more treatments compared to other animals.
Humans:
As to why humans are so comparatively unresponsive, it is not known to Kayte. In her words, “It seems like the only advantage of standing up was to free our hands to shove food in our faces”. This advantage of becoming bipedal is arguably proved through daily utilization, perhaps too much at times (holidays specifically it seems). One could theorize infinitely on factors contributing to this responsiveness such as genetic, lifespan, and cognitive interactions, but this is well beyond the scope of this article.
Picking back up on our concept of life and Osteopathy being integrated, in this same sense we can utilize problem-solving applied to different animals by examining the structure/function relationship. We can compare animals’ anatomy (structure) and determine how their anatomical nuances inform us of their function. Conversely, we can attempt to understand an animal’s specialized skillset (function), theorize the anatomy they would need to make this possible (structure), and then compare it to reality. An advantage of current technology is that we can easily visually/digitally display the same body parts from different animals side-by-side. While high-end programs are always available, you might find that MS Paint works just fine for quick, day-to-day displays.
As a primer, it is noteworthy that many animals have similar structural configurations: a large middle section we might call a “trunk”, a head that contains a larger nervous structure, and four appendages extending off the trunk. In addition to structural similarities, animals have evolved under many of the same environmental conditions, such as earth terrain, hunter/prey relations, reliance on air consumption, and constancy of gravity. While many of these conditions might seem obvious, it is important to remember that, as much as animals diverge in some ways, they have needed to adapt to similar conditions and so we should expect some shared structure/function relationships.
According to Kayte, we can start by asking a simple question: “What is your job, cat?” or “What is your job, dog?” (You do not have to say this to a real-life animal, though it is an enjoyable experience when possible)
We can then be more specific, asking “What is your job, paw?” or “What is your job, tail?”
The job or task that the appendage is suited for likely suggests that the animal evolved in, and is adept at surviving in, a particular environment. To use a common example, we know that flippers are not as useful as fingers on dry land but add quite a bit of speed underwater.
When we’ve determined more specific function(s) of a part we then ask: “How does that relate to what the human uses that part for?”
This questioning series is a useful thought process for starting to understand the integrated anatomy of animals and is very possible to do as a mental exercise without a real animal present.
In the spirit of everything outlined above, I have drawn up three examples based on relatively well-known animals. As this is not an in-depth analysis, the parts and comparisons will be kept small and simple. I am an amateur and will attempt my best, but there will likely be mistakes and misinterpretations. Hopefully I will not lead the readers too far astray.
The Rib Position in the Horse
This example was specifically suggested by Dr. Armstrong, as it is a relatively easy point of comprehension. Kayte largely explained this anatomic relationship to me and so I cannot take credit for more than recording and illustrating.
The ribs of horses (and many other four-legged animals) are positioned perpendicular compared to humans’ ribs. Notice that the horse’s ribs are suspended in the coronal plane and attached vertically off the spine whereas human ribs are suspended roughly in the transverse plane.
The “job” of the ribs in both animals is to assist with the movement of air into and out of the lungs. The multi-planar expansion and collapse of the ribs create a vacuum for inhalation as well as a pump for exhalation, all while assisting with several physiologic processes. In humans, exhalation is very easy as the ribs are naturally being pulled down by gravity. Inhalation, however, works against gravity due to the orientation of the human ribcage. This is very much the reason we have numerous muscles to facilitate inhalation, but far fewer to facilitate exhalation.
Inhalation is much easier for horses and other quadrupeds, as they are able to “swing” the ribs anteriorly (forward) as they are “hanging” vertically from the vertebrae. In the same way, exhalation occurs in the opposite direction, moving perpendicular to the pull of gravity as well. We can also theorize that the act of inhalation is enhanced by a quadruped’s gait cycle, as extending the legs forward creates expansion of the entire trunk at once.
Gorilla Ilia vs Human Ilia
The gorilla is an apt comparison, as they can walk in a similar fashion to humans and are widely recognized animals. While humans are more closely related to chimpanzees and bonobos than to gorillas, the latter two are not nearly as immediately recognizable to the average reader.
Notice that the pelvis of the gorilla is longer vertically when shown next to a human pelvis. A larger and more robust pelvis can, in part, be explained by the gorilla’s larger size and muscular density. Furthermore, we can look at the gorilla’s general posture to explain this proportion difference. While the human stands upright, the gorilla tends to be in a leaning position when sitting or ambulating. The elongation of the ilia in the gorilla pelvis makes more sense when we take posture into account, as there would be a constant pull on the ilia through the muscles of the back.
Kangaroo Pubic Symphysis in Comparison
We likely don’t think there are many similarities between kangaroos and humans, but they do share at least one commonality: like us, kangaroos are bipedal. Though the kangaroo’s method of locomotion is very different from a human’s, they both move on two feet, not four. Animals that are similar to humans in some ways and dissimilar in others are helpful examples for comparing the anatomy.
To start, notice the width and joining of the pubic symphysis in the kangaroo’s pelvis compared to the human and the gorilla.
Thinking from structure to function, the kangaroo’s thicker pubic symphysis suggests that a great deal of weight-bearing occurs here. If we visualize the way a kangaroo moves, hopping on its hind legs, we can deduce that there would be significant compression at the pubic symphysis joint each time it lands. The kangaroo’s bouncing travel style would result in significant impact forces travelling up the legs each time they land. These forces pass through the hip joint into the pelvis simultaneously on both sides due to the two-legged hop. Some of this force passes posterior to the pelvis but some will travel through the pubic symphysis, pushing it together or compressing it.
The kangaroo would also need a strong set of adductor muscles to keep the legs in (adducted) when thrusting off the ground and when landing. We can assume these adductors, as well as their attachment point on the pubic bone, need to be quite large and robust to support the substantial weight of the kangaroo’s upper body and tail.
As interesting and educational as this exploration into comparative anatomy is, it can also be a fun exercise for the practicing Osteopathic Manual Therapist to look at anatomy in a new way. The author hopes that this mental exercise was entertaining, in addition to being useful and thought-provoking.
I would like to thank Dr. Kayte Armstrong for taking the time to meet and educate me on some very interesting topics. It is rare to have the opportunity to speak with someone with so much experience coupled with so much passion.
Dig on.