A horses conformation is the way it is made up, its structure, how its body parts relate to each other and how it is proportioned. Historically its assessment has been a largely subjective practice with the formation of anecdotal relationships between certain characteristics and certain abilities. There is emerging a new way of assessing conformation in the dynamic realm, until now conformation has largely been assessed statically, assessing the angles and proportions of the horse stood still, but new research has questioned the accuracy of static assessments correlation with injury and attributes the predispositions rather to dynamic conformational markers, however this study expressed the continued importance of static conformation. Conformation influences how the forces of locomotion are distributed through the horses structures, their musculoskeletal system has to cope with as much as 2.5x their body weight going through their limb at a gallop! And they need to cope with this, cycle after cycle, which becomes cumulative, leading to cyclic overloading as the structures become progressively weaker (Weller 2019). Taking this into consideration we can see how all three of the conformational parameters need to be ideal to effectively dissipate those kind of forces, and the links between certain conformations and their predispositions are widespread. Conformation can be put into three different sets of parameters,
Macro conformation – The widely recognised recognition of the angles created by the horses limbs, the relationship between joints, essentially looking at the horse as a series of levers and pullies.
Micro Conformation – This is looking at the make up of the internal structures, their thicknesses and elastic modulus as different characteristics will cope with biomechanical forces better or worse.
Dynamic Conformation- These are individual locomotive characteristics of the horse, stride length and leg stiffness for instance, these parameters influence the amount of force exerted on the musculoskeletal system.
More information on dynamic conformation can be seen at this link, this is also a reference for some points made earlier.. https://youtu.be/W115iyCT_ck
A study that helps explain the implications of dynamic conformation is that of Hobbs et al (2018)
This image created by the author expresses the findings of Hobbs et al (2018). The high low hoof conformation results in asymmetrical propulsive forces, due to both the macro and micro conformational differences between a pair of fore feet, this also effects the entire musculoskeletal system. Read more at
Conformation is not a fixed entity, it changes with age, work load, pathology, stance or posture and other congenital factors, and can of course be influenced by human intervention. This is not truer anywhere than in the hoof which morphs according to the forces acting upon it, Bowker (2003) found that the hooves of horses up to the age of around 4-5 were very similar in makeup. The hoof is also an area where we can look to further understand the micro conformational factors. Lets take the anti-concussive mechanisms of the hoof, designed to be the first port of call in force dissipation, the frog, digital cushion, lateral cartilages and vascular structures of the hoof. Even if two horses have the same macro conformational markers these internal structures may present quite differently and can help explain why one may fail and not the other. Bowker (2003) goes into depth studying the micro conformational markers and found distinct differences in “good” and “bad” footed horses, it expressed how important the areas listed above were in bearing load so other structures not designed to bear load were protected.
Bowker (2003) showing the vast differences there can be in micro conformational markers, these differences equate to ability to withstand cyclic load and force dissipation. The fibro-cartilage content for example is stated as being important in force dissipation due to its proteoglycans.
This image from Bowker (2003) shows the comparison between a “good” and “bad” foot. Note the increased vascularity within the lateral cartilages in the “good” foot.
These two images, although slightly different sections, show the difference in micro conformation. Note the differences in the size of the digital cushion and the frog and the vascular inclusion of the lateral cartilages. You can also see the difference in fibrocartilage content of the cushion. These structures influence the shape of the hoof and its haemodynamic properties. Courtesy of Lindsey Field. More of these great images can be seen at this highly recommended educational page.
Bowker (2003) also goes on to discuss the link between macro and micro conformational markers, expressing that feet with underrun heels bear weight further under the pedal bone, therefore not utilising their haemodynamic shock absorbing system, putting the heels, bones and ligaments under excess strain. You can see from the Bowker (2003) images that the bad foot having less re-enforcing structures would be more likely to collapse as well as have less effective concussion dampening mechanism, predisposing to concussive injury.
Understanding Hooke’s law and Youngs modulus of elasticity helps us understand how these structures fail when they exceed their elastic modulus by taking unintended (or excessive intended) load.
This is a representation of these laws applied to two different hooves with different elastic modulus’, another micro conformational marker. Note the different deformation rates and fracture points.
Hooke’s law, F=kx, and Youngs modulus of elasticity, state that the deformation of an object is directly proportional to the force applied to it, up until the point at which the elastic modulus is reached when the material begins to fail and eventually fracture. Different materials will have a different stress-strain relationship depending on the stiffness of it structure, just as two different hooves will have the same difference in their stress-strain graph. This tells us the makeup of the individuals hoof structures will react differently to forces applied on them, some feet inherently can cope with force more efficiently than others and therefore return to form after force application more easily and at higher forces. So we can see that two horses with the same external markers at the beginning of a training regime could end up with quite different macro conformations after, due to how their micro conformation responds to the work. This law can be also be applied to the tendons, certain conformations will be more likely to cause a tendon to exceed its elastic modulus, showing the importance of farriery intervention in these cases.
The subject of disordered physiology and hoof morphology can be read further at this link.
This picture shows how the micro conformation has failed, the elastic modulus of the heels has been exceeded and they have collapsed, this directly effects the macro conformation, which has effects on the entire musculoskeletal system, pushing structures close to their elastic capacity. This has been improved through farriery intervention.
Farriery can have a direct effect on all three conformational parameters, both positively and negatively, the micro conformation needs to be understood and looked after, but if and when this fails the macro conformation can be corrected which often then leads to improvement of the micro conformation, both of which will play a role in the biomechanics of dynamic conformation, understanding this relationship is important in farriery practice! The response that “that is just its conformation” is outdated, leaves the horse vulnerable to predispositions and prevents the horse from receiving care that could result in positive morphology.
Something that is also important to take into consideration is the difference between posture and conformation, and their relationship with one another. A stance adoption or gait adaption in response to pathology can have a direct effect on conformation. See my article on recognising pain.
Recognition of compensatory mechanisms is important in maintaining or creating the ideal.
This image shows a posture adopted to relieve spinal pathology, the question of which created which is still unanswered but regardless there was a clear link with the presenting hoof conformation which showed the failure of the micro conformation in withstanding the load. This stance represents the horses conformation at a point in time, but farriery, surgical and physio intervention created the ideal conformation seen on the right.
This brings the author onto the re-occurring theme through all his articles of Holistic, pro-active farriery. Recognising the conformation that presents is important and understanding that the ideal is the ideal because it means correct loading of the entire musculoskeletal system encourages the farrier to provide interventions to create that ideal. What also must be remembered is that normal or common does not constitute ideal! The author has created an adaption of Mawdsley et al (1996) to aid in objectively assessing the horses static macro conformation in his care. It is a farriery related conformation scoring system that uses the established ideals as a reference point, used for establishing farriery and other practitioner interventions. Static Macro conformation gives a good indication of what will be seen at mid stance of locomotion, when the limb is fully loaded, although Weller (2019) adds dynamic conformation to this equation.
This is one of the conformational markers in the objective farriery related conformation system created by the author, adapted from Mawdsley et al (1996). When we start to actually grade what we see, without bias, we can no longer ignore that we need to intervene. If this score is taken at every shoeing it shows the farrier whether things need to be changed, as they should be looking to always create or work towards the ideal.
Using this slide as an example, the micro conformation of the 1 has failed, the heels are weak and have exceeded their elastic modulus, it most likely has a poorly conformed digital cushion, predisposing to navicular to name one pathology. Interventions have to be made to address these observations, de-load those structures to bring them back within their elastic modulus and you will begin to work toward the 4. This can be done by providing frog support and padding for example, acting like an artificial digital cushion.
Read my articles on frog support and wedge pads for further reading.
This is only one example of a much bigger picture, farriers and indeed everyone working with horses, should look at the horse as a whole, its static, macro and micro conformations and its dynamic conformation, if we see that the conformation is compromised we need to understand what parameters we can have a positive effect on and what parameters we are simply managing. Understand the importance of intervention in mitigating predispositions, and no longer accept the conformations that we can affect as “just how it is”. To do all of this you must look, objectively. Our understanding of conformation and biomechanics is an evolutionary process and continues to be researched, what is important is that this research and its implications makes its way into everyday practice and underpins the ethos of our protocols.
The farriery related, objective conformation assessment system is available for purchase from the author and clinics on farriery related conformation are also available. Contact the Author at
theequinedocumentalist@gmail.com
References
The role of conformation in musculoskeletal problems in the racing Thoroughbred
First published: 05 January 2010
Contrasting Structural Morphologies of “Good” and “Bad” Footed Horses
Robert M. Bowker, VMD, PhD
Weller, 2019, https://youtu.be/W115iyCT_ck
Linear assessment of the Thoroughbred horse: an approach to conformation evaluation
First published: November 1996
Hobbs. S, Nauwelaerts. S, Sinclair. J, Clayton. H, Back. W, 2018, Sagittal plane fore uneveness is associated with fore and hindlimb asymmetrical force vectors in the sagittal and frontal planes, Plos one, https://doi.org/10.1371/journal.pone.0203134
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