If you have ever listened to your farrier or veterinarian explain information about your horse’s foot and were completely confused, you are not alone. AND this blog post is for you!

The unique anatomy of a horse’s foot (one digit bearing all the weight) and lifestyle (spends the majority of the day standing, including during sleep) makes the health of a horse’s foot paramount to horse health. This is why your farrier and veterinarian will often work together in order to come up with solutions when a horse is uncomfortable.

The following is a list of terms commonly used by farriers and veterinarians to describe the conditions within the hoof capsule. Since I am a veterinarian, this is written in terms of what you can see when radiographing (X-raying) the hoof. However, radiographs are not always available. For an experienced farrier, visual examination of the hoof can provide insight into the overall state of the foot which then can be confirmed through radiographs.

1. Sole Depth

Sole depth refers to the distance between the tip of the coffin bone (last bone in a horse’s foot) and the sole of the foot. Due to the concavity on the sole of most horse’s feet, this is not the same as the distance between the tip of the coffin bone and the ground. Most veterinarians and farriers will agree that this distance should be greater than 1.3 cm to 1.5 cm in your average horse.

Why is this important for hoof health?

Sole depth is important because thin-soled horses will often be uncomfortable on hard ground or traveling over gravel. Horses with thin soles are particularly prone to bruising and with enough force, the tip of the coffin bone can become inflamed and irritated causing a condition referred to as Pedal Osteitis. Horses with sinking laminitis (founder) will have their sole depth decrease due to the inflammation within the soft tissue around the bone, resulting in the coffin bone sinking closer to the ground.

  Here is an example of a horse with thinning sole depth due to rotation and sinking associated with laminitis.

Here is an example of a horse with thinning sole depth due to rotation and sinking associated with laminitis.

2. Breakover

Breakover refers to the period of time between when a horse’s heel lifts off the ground and the toe lifts off the ground. The point of breakover is the specific site on the ground surface of the foot or shoe where that occurs. This point can be adjusted by the farrier by either grinding down the shoe to bring this back or accomplished on a unshod foot by rolling the toe with a rasp. Breakover does not just occur from front to back, but there is some degree of breakover on the side of the foot as well when the horse is turning corners or based on the angulation of a horse’s limbs.

Why is this important for hoof health?

A good breakover point on a shoe can eliminate extra stress placed on structures within the foot and the nearby joints, ligaments, and tendons. This can be particularly important in horses with palmar heel pain (navicular syndrome) or laminitis. By adjusting the breakover, a farrier is essentially adjusting the amount of time the horse’s foot is on the ground which can help relieve pathology or issues within the foot. However, it can also change the stride of the horse. For this reason, breakover a point of contention between various equine professionals. Used correctly, it is an amazing tool to help horses heal and avoid unnecessary stress within the foot.

For more information on breakover, this article from The Horse breaks it down nicely: The Basics of Breakover

3. Hoof-Pastern Axis

The hoof-pastern axis (HPA) is the alignment of the dorsal hoof wall (front aspect of your horse’s hoof) and the front aspect of your horse’s pastern when viewing from the side. When the horse is standing square, these two lines should be parallel in a correctly trimmed foot. A horse that has a broken-back HPA has a shallower angle to the dorsal hoof wall than that of it’s pastern (long toe, underrun heel), whereas a horse with a broken-forward HPA has a more upright or steeper angle to the dorsal hoof wall than that of it’s pastern (in severe cases, these are referred to as club feet).

Broken-Back HPA

  Photo:   http://www.thehorse.com/articles/36890/long-toe-low-heel-hooves-let-them-grow-naturally

Photo:  http://www.thehorse.com/articles/36890/long-toe-low-heel-hooves-let-them-grow-naturally

Broken-Forward HPA

  Photo:   http://www.equipodiatry.com/article_flexural_deformities.htm

Photo:  http://www.equipodiatry.com/article_flexural_deformities.htm

Why is this important for hoof health?

Horses with a broken-forward HPA experience extra stress on the coffin joint (the coffin joint is in flexion constantly) and as a result, extra strain is placed on supporting ligaments of the fetlock joint. Horses with a broken-back HPA experience extra stress on the coffin joint as well (in this case, the coffin joint is in extension constantly), resulting in extra strain across the deep digital flexor tendon, navicular bone, and surrounding soft tissues.

Radiographs are very helpful in developing shoeing or trimming solutions with horses that have variations in their hoof-pastern axis. Ideally, the the line drawn down the dorsal hoof wall, the angle of the heel, and a line drawn through all three bones within the horse’s foot (three phalanges) are all parallel. This alignment allows for the most physiologically normal foot and prevents potential sources of lameness. This is not always feasible in all horses depending on their conformation.

For more information on hoof angle, see this article from veterinarian and farrier, Dr. Stephen O’Grady: Hoof Angle

4. Lamina

The lamina (also known as lamallae) refers to the soft tissue that is between the hoof wall and the bony structures within the hoof capsule. This specialized tissue has long finger-like projections that interlock with inner surface of the hoof horn to provide a firm attachment and support the weight of the horse.

Why is this important for hoof health?

When the lamina becomes inflamed, it is referred to as “Laminitis.” Most horses that are affected by laminitis are in extreme pain and unwilling to move, lying down or leaning back to try to remove pressure from their front feet. Prolonged or chronic laminitis can lead to rotation or sinking of the coffin bone within a horse’s hoof capsule. In severe cases, the coffin bone can sink far enough that it will protrude through the sole of the foot. Laminitis can be the result of metabolic disturbances (most commonly Equine Metabolic Syndrome or equine Cushing’s disease, also known as PPID), traumatic concussion (road founder), or systemic disease (secondary to endotoxemia or extremely ill horses). Laminitis can occur in all limbs or just one, but most commonly affects both front feet.

5. Palmar Angle

The palmar angle is the angle created between the solar margin of the coffin bone (bottom of the foot when viewing from the side) and the ground surface. Many veterinarians would agree that this angle should be between a positive 1 to 5 degrees, with 3 to 5 degrees being ideal. That being said, the actual measured palmar angle is less important than what it represents in terms of alignment of the bony column within the hoof capsule (see hoof-pastern axis). If the bones within the foot are well aligned, the horse will likely be comfortable despite the actual measurement of their palmar angle.

Why is this important for hoof health?

Horses with a negative palmar often have a broken-back hoof-pastern axis and can be sore to hoof testers across the heel. This sort of alignment can create extra stress and pressure on the heel of the foot (navicular bone and surrounding ligaments). A horse with too high of a palmar angle will often have a broken-forward hoof-pastern axis which can place strain on the coffin joint and suspensory ligament.

  Here is an example of a horse with a low palmar angle. This horse was sore to hoof testers across the heel

Here is an example of a horse with a low palmar angle. This horse was sore to hoof testers across the heel

If you have a question about your horse’s hoof health, please give us a call to schedule your appointment with Badger Equine Veterinary Services.

For more information on these topics, please see the following resources: