The hoof is the horse's foundation. Although it appears to be one solid body part, the hoof includes both exterior and interior structures that work together as the horse moves. By reviewing each piece of horse hoof anatomy, you can gain a better understanding of how it functions and why problems may occur.
Exterior Anatomy
The exterior hoof structures support and protect the interior structures. Download this PDF by clicking on the image, to see an exterior anatomy diagram and each structure's placement in the hoof. For any problems with Adobe, refer to this guide for troubleshooting.
Wall
The hoof wall is a weight-bearing structure that grows from the coronet band. It's the exterior-most portion and the part of the hoof that you see when you look at a horse's foot. It is made of keratin, similar to a human's fingernail, and has a low moisture content, making it hard. The wall is essential because it protects the vulnerable interior structures of the horse's hoof. It has three layers: outer (called the periople), middle, and inner layers.
The wall grows continuously, so a horse needs regular trims from a farrier to keep the hoof shaped correctly. Overgrown or poorly maintained hooves can lead to lameness or even prohibit a horse from walking. Signs of an unhealthy hoof wall include cracks, ridges, rings, and overgrowth.
Coronet Band
The coronet band, also called the coronary band, is at the top of the hoof at the junction of the wall and the leg's hairline. About 70 percent of new hoof growth generates here. To support this growth, the coronet band has a large supply of blood vessels. Injuries to this band can result in interruptions in growth or even permanent problems.
Sole
If you take a look at the underside of hoof, you'll see the sole. It runs from the bars to the frog and never makes contact with the ground. Low moisture content makes it feel hornlike, but it is softer than the rigid hoof wall. The sole is concave, and its purpose is to protect the interior structures and support the wall.
Just like the wall, the sole grows continuously. Keeping a horse properly nourished with a balanced diet and enough exercise will help keep the soles thick and healthy. Genetics as well as environment play roles in a horse's sole health. Discomfort and lameness can occur if this structure doesn't develop properly or sustains an injury.
White Line
The white line is technically a structure within the sole where the sole meets the wall on the bottom of the hoof. Looking at the underside, you can see this is the line where it forms a shallow groove. Despite the name, the white line is actually more of a yellowish shade.
It seals the coffin bone within the hoof and protects it from infection. If the white line isn't healthy, bacteria or fungus can enter in between the layers of the hoof wall and an infection can occur. Although this infection doesn't actually involve the white line, it's called "white line disease."
Frog
The frog is a rubbery V-shaped structure that distributes impact to the plantar cushion as the horse moves. It also provides traction on uneven surfaces, absorbs shock, and protects the horse's digital cushion. It possesses a great number of blood vessels and nerve endings. These qualities make the frog vital for coordination and allow a horse to know where they are placing their foot on the ground.
When it comes to hoof care, the frog is one of the most important structures to keep healthy. However, it does not need to be trimmed.
Collateral Grooves
Collateral grooves are the channels that run along either side of the frog. Their depth is proportionate to the sole's thickness, so equine owners and veterinarians carefully measure the collateral grooves to monitor sole thickness and health. These fill with dirt as the horse moves, providing traction.
Bars
The bars are extensions of the hoof wall that act as weight-bearing structures to prevent the heel from distorting. They also keep the wall in a semicircle shape. To visualize the bars, you can look at the underside of the hoof and see that they begin at the heel and angle inward, running alongside the frog. It's harder than the sole, which is how you can differentiate the two.
Just like the rest of the hoof wall, bars experience new growth. In fact, they grow more rapidly than other portions of the wall, but the topic of whether bars should be trimmed regularly is a controversial one.
Heel Bulbs
Heel bulbs are similar to a human's hand at the base of the thumb, and reside at the back of the hoof. They are soft tissue and enclose the digital cushion, which provides shock absorption and enhances circulation. They contain blood vessels, connective tissue, and sweat glands. This sensitive tissue is at risk for injury from kicks or cuts on objects or fences.
Interior Anatomy
Many of the interior structures include bones and tendons. These absorb concussion, preventing injury as the horse moves. Download this interior anatomy diagram to see the inside of the hoof.
Pastern
The pastern, which begins in the hoof and ends at a horse's fetlock (comparable to the wrist or ankle in a human), is made up of two separate bones.
- Long pastern: The long pastern bone, sometimes called the proximal phalanx, is the top piece of the pastern joint. This bone absorbs concussion as the horse moves.
- Short pastern: The short pastern, or middle phalanx, is the lower piece of the pastern joint and the top piece of the coffin joint. This bone has rounded ends so that the hoof can rotate side-to-side on uneven ground.
Coffin Bone
The coffin bone, also called the pedal bone or distal phalanx, is the main bone that makes up the hoof. It varies in shape between the front and hind hooves. Front hooves have wide, round coffin bones, while hind hooves have narrow, pointed coffin bones. Because this bone's shape determines the hoof's shape, it affects how the horse moves.
In the front, its shape allows the horse to break over the center of the hoof as they move. In the hind, it allows the horse to turn. The digital flexor tendon attaches to it. The coffin bone has the hard hoof wall to protect it, but it's still possible for this bone to become fractured or injured.
Navicular Bone
The navicular bone is a small, flat bone that sits behind the coffin bone and under the short pastern. The deep flexor tendon runs underneath it before attaching to the coffin bone, so it works like a fulcrum on the tendon as the horse moves. This prevents the coffin joint from over-articulating. When this bone becomes damaged, it's known as Navicular Syndrome, which is a very painful condition.
Tendons
There are two primary long tendons that contribute to proper hoof function. These vital structures can become injured due to trauma or overuse, and restricted activity for extended periods is required for healing.
- Extensor tendon: The extensor tendon runs along the front of the hoof and and allows a horse to straighten the coffin and pastern joints. This keeps the horse from "knuckling over" by extending the leg.
- Flexor tendon: In contrast to the extensor tendon, the flexor tendon runs from the knee along the back of the leg to the hoof. It allows the horse to bend the coffin and pastern joints.
Plantar Cushion
The plantar cushion, also called the digital cushion, is above the frog. Its springy material expands and contracts to dissipate shock as the horse moves. When this cushion does not function properly and becomes atrophied, it can result in a horse being "flat footed."
No Hoof, No Horse
Proper hoof care and prompt attention to hoof problems are important aspects of keeping your horse sound. The hoof is a complex structure with each part working in unison, so when one part is compromised, the horse cannot perform their best and may suffer permanent lameness.
