Arena Surface Impacts Fetlock Kinematics in Extended Trot

Arena Surface Impacts Fetlock Kinematics in Extended Trot

One of the most common injuries dressage horses suffer is to the suspensory ligament, which plays a major role in supporting the fetlock during weight-bearing.

Photo: Chefsna/Wikimedia Commons

Researchers have made great strides in understanding how footing surfaces impact racehorses’ limb kinematics. For example, Susan Stover, DVM, PhD, Dipl. ACVS, and colleagues have learned that the forces that impact racehorses’ legs are higher and fetlock extension is greater on dirt than on synthetic surfaces. Additionally, they’ve found that racehorses’ musculoskeletal injury rate correlates with the surface—dirt is associated with a higher risk of injury than is synthetic footing.

But, of course, it’s not just racehorses that work on different footings and could be at risk of injury on those surfaces. As such, Stover, professor of anatomy, physiology, and cell biology at University of California, Davis (UC Davis), along with Jill Thornton, DVM, of UC Davis’ JD Wheat Veterinary Orthopedic Research Laboratory, and colleagues looked at whether footing impacted dressage horses’ fetlock kinematics during the extended trot. Stover presented the group’s research at the 2016 American Association of Equine Practitioners’ Convention, held Dec. 3-7 in Orlando, Florida.

“Dressage requires unique, extreme movements,” Stover said, “and repetitive movements can result in occupational injury.”

One of the most common injuries dressage horses suffer is to the suspensory ligament, which plays a major role in supporting the fetlock during weight-bearing, she said. Many factors impact fetlock motion and suspensory elongation, including the hoof-ground reaction force (GRF; an increased GRF increases the force on the structures, stretching the suspensory further, she said). An arena surface’s characteristics affect the magnitude of the GRF.

So, to gain a better understanding of how surface impacts fetlock kinematics, Stover, Thornton, and colleagues evaluated six upper-level dressage horses ridden by their regular trainers as they worked on both dirt and synthetic surfaces.

Key findings included:

  • The surface with the greatest impact force (related to GRF) had the greatest fetlock extension;
  • The synthetic surface’s maximum impact force was 41% greater than the dirt surface’s;
  • Horses had greater fetlock extension (2° more) when working on the synthetic surface than on dirt;
  • Horses had longer slide duration, shorter support duration, and faster breakover on the synthetic surface than the dirt surface, which is typical on harder surfaces; and
  • Horses’ hooves slid backward more on synthetic than dirt during support phase of stance, which indicated the dirt provided better support for the horse to push off for propulsion than the synthetic surface.

As such, Stover confirmed that “surface properties have the potential to affect risk for suspensory ligament injury. However, surface properties cannot be assumed from the surface materials alone (that is, synthetic or dirt). Surface behavior is impacted by factors other than material, including structure and management.”

She cautioned that this study’s results are limited to the two specific surfaces studied and can’t be extrapolated to other footings.

“However, the mechanical behavior of surfaces clearly affects limb motions and risk for injury,” she said.

About the Author

Erica Larson, News Editor

Erica Larson, news editor, holds a degree in journalism with an external specialty in equine science from Michigan State University in East Lansing. A Massachusetts native, she grew up in the saddle and has dabbled in a variety of disciplines including foxhunting, saddle seat, and mounted games. Currently, Erica competes in eventing with her OTTB, Dorado.

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