Hoof Care and the Coffin Bone

Understanding the form and function of the distal phalanx is vital to keeping horses sound

The distal phalanx, also known as the third phalanx, coffin or pedal bone, seems fragile, lying suspended above the sole, encapsulated by the outer hoof wall and supported by an intricate web of anatomical structures. It can be likened to the tip of one finger or digit and is a critical piece of the equine anatomical puzzle.

Role As A Pump

The distal phalanx is not only a major contributor in the weight-bearing process, but also functions as a catalyst in the hoof mechanism supporting blood flow.

Some research suggests the blood flow provided by this hoof mechanism alleviates much of the work the cardiac system otherwise would have to do. Since horses have small hearts in relation to their size, its importance in this respect is critical. The foot, in effect, acts as an auxiliary heart pump, expanding with each stride and allowing the coffin bone to descend and the solar corium to fill with blood, which is then forced from the hoof and up the leg as the weight-bearing foot leaves the ground.

For a horse to stride freely, the hoof must be able to withstand the majority of concussion. The frog first contacts the surface and absorbs the initial shock; the heel buttresses and bars follow, transferring more of the energy to the flexible lateral cartilages, so that when the sole starts to shift energy to the coffin bone, much of it already has been absorbed. By the time the hoof wall at the toe is engaged…

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Toby Raymond

Toby Raymond is a horse owner and freelance writer who lives in Vermont. She is a frequent contributor to American Farriers Journal.

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