Foot Imbalances and Hind-Limb Lameness in Horses

Issues and imbalances with horses’ hind hooves might be to blame for a variety of hind-limb lamenesses. Read more in this article from the Fall 2023 issue of The Horse.
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managing horse hoof balance and capsule distortion; Farrier Trimming Horse Hoof
Therapeutic trimming and shoeing to correct hoof imbalances should aim to gradually realign the foot while providing support as long as the horse needs it. | iStock

Horses that are lame in the hindquarters might swing out their hind legs, have side-slipping saddles, or resist certain movements or directions. In more severe cases they avoid placing pressure on the affected limb. The cause might be a stifle injury, a tendon issue, hock problems, or a variety of other sources of pain. But new research suggests some hind-limb lamenesses might be associated with imbalances in the hind hooves.

Specifically, when a hoof or its internal structures (i.e., distal phalanx, better known as the coffin bone) tilt the wrong direction, it could cause foot pain leading to lameness. Perhaps more importantly, such imbalances can also lead to issues higher up in the limb, creating problems across the bones, joints, and soft tissues. These pathologies occurring secondarily to the primary foot problem can create hind-limb lameness that often looks like it has nothing to do with the feet, even though the foot is the origin of the problem, says Tracy Turner, DVM, MS, Dipl. ACVS, ACVSMR, of Turner Equine Sports Medicine and Surgery, in Big Lake, Minnesota.

The Distal Phalanx Angle and the Broken-Back Hoof Axis

Shaped like a mini-hoof and suspended in space behind the hoof wall by lamellar tissues, the coffin bone should—in theory—have a front surface that runs parallel to the hoof wall. Its bottom surface, meanwhile, should slant slightly downward (toward the front tip of the bone) compared to the ground. In other words, the healthy position of the coffin bone includes a very mild ­positive angle of about 2 to 5 degrees, explains Lynn Pezzanite, DVM, MS, a postdoctoral scholar at the Colorado State University (CSU) College of Veterinary Medicine & Biomedical Sciences, in Fort Collins.

The foot’s external shape doesn’t always reflect what’s going on with the coffin bone, she says. To get a better view, veterinarians can use X rays to visualize and calculate the relationship between the bottom surface of the coffin bone and the ground, known as the plantar angle of the distal phalanx (PADP).

If the bottom surface of the coffin bone is parallel to the ground, it’s a neutral PADP. If it’s tilted back—the tip of the coffin bone is higher than the back end, like it’s lifting up at the toe—that’s a negative PADP. Neutral PADPs have an angle of 0 degrees; negative PADPs have increasingly higher numbers depending on the severity of the angle.

Horses with negative or neutral PADPs have what’s known as a broken-back hoof axis, Turner says. That’s problematic because it causes the hoof to stay on the ground longer than normal during a step. As a result the deep digital flexor tendon (DDFT) experiences far greater strain than it should before the heel finally lifts.

“I mean, the foot’s backward,” he says. “So instead of tilting down, the bone’s tilting up, which puts tremendous strain on the flexor tendon. It just lengthens the whole leg so it doesn’t move quite as nicely as it should.”

Mediolateral Imbalances

In the front hooves, outside walls tend to grow higher than the inside walls, says Turner. “But on the back foot, what we saw was just the opposite,” he says

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We at The Horse work to provide you with the latest and most reliable news and information on equine health, care, management, and welfare through our magazine and TheHorse.com. Our explanatory journalism provides an understandable resource on important and sometimes complex health issues. Your subscription will help The Horse continue to offer this vital resource to horse owners of all breeds, disciplines, and experience levels.

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Passionate about horses and science from the time she was riding her first Shetland Pony in Texas, Christa Lesté-Lasserre writes about scientific research that contributes to a better understanding of all equids. After undergrad studies in science, journalism, and literature, she received a master’s degree in creative writing. Now based in France, she aims to present the most fascinating aspect of equine science: the story it creates. Follow Lesté-Lasserre on Twitter @christalestelas.

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