Exercise Study Reveals Anatomical Potential for Fetlock Injury

Previous studies have shown that bones develop to suit the purpose routinely required of them; therefore, would young horses in regular work from the time they are foals have stronger musculoskeletal tissues then those left to mature in pasture? Chris Kawcak, DVM, PhD, Dipl. ACVS, and the Global Equine Research Alliance researched this issue. Kawcak presented their findings regarding osteochondral tissues at the 15th Annual Kentucky Equine Research Conference.

The group divided 33 Thoroughbred foals into exercise and pasture groups. The exercise group was conditioned five times per week from ten days to 18 months of age, increasing the speed of the workouts over time as the foals grew. This group of foals was turned out in pasture when not in work. The other group also grew up in a pasture environment, but was not asked to work.

Study results were mixed. The researchers used a technique called confocal laser scanning microscopy, which scanned the horizontal layers of cartilage and showed live and dead cells as points of different color. This technology showed that the horses in the exercise group had 14% more viable cells on the surface of the cartilage in the fetlock joint, which was the area under scrutiny in this study. However, this difference in cell makeup did not appear to have any effect on the cartilage's function or structure.

While the data on osteochondral tissues did not show a strong trend for or against early exercise, the research did reveal an anatomical anomaly that could be a major factor in catastrophic injuries.

Horses in both groups showed a marked density pattern that might help to explain why condylar fractures occur. Within the fetlock joint there is a prominence of bone called the sagittal ridge. Researchers found that bone density and cartilage quality are at their worst in the parasagittal grooves (depressions on either side of the ridge)--precisely where the majority of condylar fractures occur. This finding was consistent in both the exercised and pastured groups of young horses. Cartilage in this area also showed degeneration, leading the researchers to conclude that this is an area prone to damage, and that early exercise was neither protective nor damaging to that area.

The researchers measured bone density using a computed tomography (CT) scanner, with files exported to a custom-designed program for three-dimensional analysis of the joint. This program allowed the researchers analyze disarticulated joints from all angles.

"I don't know that there's anything we can do to protect that condylar area," Kawcak said. "But at least we know (exercise) didn't hurt them."

While this report covered only the osteochondral tissues, results of the tendon and ligament analyses are pending. Half of the horses from each group have gone on to racing careers under a trainer who is unaware of which group each horse belonged to in the study. Kawcak says the results of that portion of the study should be available next year.

About the Author

Erin Ryder

Erin Ryder is a former news editor of The Horse: Your Guide To Equine Health Care.

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