Physiological Sequencing - A State of Flux

In a previous blog post, ‘X Rays, Beyond Balance’, KC La Pierre introduced the exercise of Physiological Sequencing. Understanding how Physiological Sequencing applies to the structures of the equine foot can help us to be more pro-active in our efforts to prevent problems from developing.

To re cap; Physiological Sequencing explains the order in which physiological processes occur.

Tissues are grouped into three types, according to the rate they respond to change: Soft Tissue, Dynamic Tissue and Static Tissue.

Soft Tissue is vascular, meaning it contains blood and nerves. Any change of stimulus to Soft Tissue will immediately change the way the horse holds himself and moves in response. Soft Tissue changes cause the horse to move either more symmetrically or more asymmetrically. Such changes affect the foot almost immediately, as change to how the horse moves will result in a change to how stimulus is delivered to the soft tissue of the foot and therefore to the second tissue in the sequence, Dynamic Tissue.

The main Dynamic Tissues of the foot are ungular cartilage and hoof horn: They are avascular structures (have no blood supply or nerves). Ungular Cartilage forms the foundation of the palmar (rear) two thirds of the foot, meaning that the confirmation of the cartilage determines the confirmation of most of the hoof capsule. The ungular cartilage and coronary band work together to suspend the internal foot within the hoof capsule. A soft vascular network of blood vessels, or ‘dermis’, sits between the internal foot and the hoof capsule. Dermis has many important functions in the foot, one of which is nourishing the horn of the hoof capsule. Confirmation and health of both the hoof capsule and the underlying cartilage, along with the application of stimulus determines how effectively the dermis is able to supply the horn with nutrients.

The dynamic hoof capsule is the vehicle for delivery of stimulus to the foot within. The confirmation of the hoof capsule and health of the horn affects both how the dermis is stimulated and how pressure is delivered to the cartilage and coronary band throughout the stride of the horse. Ungular cartilage cannot be nourished by the dermis, it requires appropriate pressure in order to develop healthily. If at any point the horse feels pain in his soft tissues, he will alter the loading of the foot to avoid the pain. This may be very subtle and if left undetected, the result will be improper development of the ungular cartilages and improper horn growth.  Physiological sequencing tells us that these changes will eventually affect the static tissue, the bones of the foot. 

Static tissue, bone, we understand is always in a constant state of flux, modelling and remodelling, however these changes can take longer for physical change to be seen. The changes are less immediately obvious than the other tissues in the foot. The pedal bone, P3, is unable to remodel due to it lacking a medullary cavity so modelling of this foundation bone of the foot is irreversible. Wolff’s Law states that cells will align themselves directly with the line of force. Using a radiograph the line of force can be seen in the density of bone cells where modelling has taken place, for instance in cases where the foot has been chronically imbalanced. Examination of the dynamic structures in the foot, together with the application of Physiological Sequencing, will point to why the Static tissue changes have occurred and how the dynamic tissues can be addressed in order to prevent further changes to bone.

All tissues of the foot are in a constant state of flux. Observing change and understanding what is correct structure and function allows us to ensure tissues are developing healthily. In his article ‘Did I do that?’, KC La Pierre describes how he identified a rider imbalance by noticing lateral flare in one hind foot of each of her dressage horses. A rehabilitation programme was put into place for the horses and the rider. This prevented the cause of the change to the Dynamic tissue of the horses from becoming the cause of bone change.

ETB Pegasus Gait Analysis technology accurately pinpoints where and when any asymmetry or irregularity of gait occurs. Soft tissue needs to be free of pain in order for the horse to move and develop as symmetrically as possible.

Early identification and treatment of pain and close observation of dynamic tissue whilst being mindful of Physiological Sequencing can increase our chances of preventing pathologies.

About the author: Penny Thorpe, DAEP came across Applied Equine Podiatry whilst working for two trainers who were clients of Trevor Jones DAEP. Curiosity to know a 'bit more about feet' led to a fascinating journey of study with the Institute, graduating as a DAEP in 2013 and starting second level study in 2014. She lives in Brighton with her family and is privileged to have a small practice of dedicated owners and lovely horses.