I think most horse owners have heard of hoof flare at some point and have probably even had their hoof care providers tell them their horses have some flaring, but is hoof flare something an owner should worry about? In my opinion, yes, it is absolutely something that needs to be addressed, because flaring can lead to pain and inflammation of the laminae, reduce the concavity of the hoof, make horses prone to white line disease and abscesses, and even cause mechanical founder. The goal of this blog series on hoof flaring is to help you understand and visualize what hoof flaring is and how it affects the structures of the hoof. Let’s get started!
Hoof flare is the result of mechanical forces prying the hoof capsule wall away from the sole region and coffin bone resulting in the golden-line and wall laminae being stretched/separated. Whoa...this is sounding a little too much like “real” engineering...I thought I gave that up to work with horses! ;) Don’t let “mechanical forces” scare you. Mechanical forces are simply forces resulting from the physical contact between two objects; in this particular case, the downward force applied on the ground by the hoof and the upward force applied by hoof onto the ground when the ground and hoof come in contact.
The image above illustrates, in my opinion, a well trimmed and balanced hoof. You will notice the capsule wall and golden-line are both touching the ground, so they are able to work in unison to support the weight of the horse. When the hoof is well trimmed and balanced, the mechanical forces between the hoof and the ground will not cause flaring. Below is an enlarged image of the golden-line and capsule wall working together to support the weight of the horse:
When the length of the capsule wall begins to exceed the length of the sole region the capsule wall is required to bear all the weight of the horse on its own. See images below showing our same illustration with excess wall height:
The excess capsule wall is not strong enough to handle bearing all the weight of the horse, so it has no choice but to break/deform in some way. In a hoof with a healthy, strong wall the hoof wall will often self-trim by cracking at last point of connection with the sole. While not always pretty, it allows the hoof to be functional and avoids the excess capsule wall creating stress on the golden-line and laminae:
In hooves with weaker, less healthy walls (overly moist, already distorted, diseased with fungus/bacteria, etc.) the excess capsule wall tubules will bend rather than crack resulting in hoof flaring. The bending of the wall tubules creates stress on the golden-line resulting in it becoming stretched and separated:
Flaring always starts near the ground, but will continue to distort the hoof wall higher and higher up as the upward force from the ground continues to push on the bent wall tubules and stretched golden-line. Eventually, the flare will get high enough to move past the golden-line and begin prying apart the insensitive and sensitive wall laminae. At this point, the flaring will be causing the horse pain as it will be stressing a sensitive structure. This is a form of mechanical laminitis—inflammation of the laminae due to improper mechanical forces.
In addition, the force of the ground onto the flared bottom of the hoof creates pressure inward towards the sensitive laminae at the top of the flare which often results in a horizontal bruise line known as a flare bruise.
The poor wall laminae is getting pulled apart and pinched at the same time...ouch!
Next, we'll go over how flaring affects the concavity of the hoof!