Part 3 of Equine Balance

In my last blog, I asked you to consider the relationship balance between the middle and distal phalanx and its consequences for the navicular bone. Did you come up with any ideas?

I would also ask if you have ever considered how the equine foot was designed and why nature has designed it the way we see it today. Do you know it was once a structure different from what you see today? The equine used to have toes, and millions of years ago, nature decided that this design did not suit the developing animal and changed it to its current structure, the equine hoof capsule and its associated structures.

I find it amazing that when we look closely at her design, we can see familiar structures and decide on their basic loading parameters and tensile strength capacity. The dome and triangle shapes are two common structures well-known in the engineering industry for their strength and load-bearing capacity. 

When we look closely at the equine foot, we can find these two structures form the basic loading structures for the distribution of weight to the ground under their feet: the domed-shaped distal phalanx and navicular bone, with the triangle shape forming the basis of the internal bars and digital cushion.

But just knowing that these two structures are present in the equine foot does not give us the full story of how they distribute the forces they are under nor how they change their functional shape when things and not equal. 

We must establish these structures' loading forces and tensile strength under stress that causes them to change shape or even shear the structure completely. This occurs in the equine foot when you have a misshapen hoof capsule, low heels, medial-lateral imbalance, dry and brittle feet, or tendon and ligament issues. 

First, the weight of the equine descends from the upper body to the distal joint of the limb, and it needs to have the middle phalanx central to the distal phalanx; otherwise, the correct articulation of the distal interphalangeal joint will not be able to transfer the weight to the surrounding soft tissue and hoof capsule. A misalignment in these two bones leads to the misplacement of the navicular bone.

When the navicular bone is misplaced, it affects the articulation of the middle phalanx with the distal phalanx and the navicular bone with the middle phalanx. With a dysfunctional articulation of the bones of the joint, you will also experience a misalignment of the flexion surface of the navicular bone with the flexion surface of the deep digital flexor tendon. This leads to the neuromuscular response of the common digital flexor muscle shortening to ensure the tension on the deep digital flexor tendon is biologically correct with the flexion surface of the navicular bone. Any dysfunction in the area of the common deep digital flexor muscle leads to the tension of the horse's elbow and shoulders, affecting many issues as the passive stay apparatus, short strides, high head and neck position, spinal pain, change in breathing patterns, the timing of the limbs breakover therefore the breakover of the hoof and many other issues if left to continue.

These upper body compensation patterns, known as chiropractic listings, then affect the loading of the distal joints of the limb, how blood can supply the functional foot and the neurological signals derived from such issues. Issues such as these and others alter how the animal loads its feet and the final shape of the hoof capsule. It affects the distal bones and can cause things like sidebone, ringbone, pedal osteitis, arthritic issues and the dysfunctional growth of the external hoof capsule. 

I am trying to keep these talks short so you have time to read them. We will continue our understanding of equine balance next month.

The relationship of the Distal Interphalangeal Joint