It is widely believed that exercise and limb-loading in foals help joint cartilage functionally adapt to the rigors of athletic activity. In 2005, Dutch researchers set out to find out if they could verify the concept of functional adaptation of cartilage by measuring the biomechanical (the mechanics of biological activity) properties of cartilage in stillborn horses, and comparing those values to those observed in horses at 5 months of age, 18 months of age, and maturity. Their work was published in the March issue of the Equine Veterinary Journal.

Two sites on the top of the fetlock joint in the forelimb were chosen for testing because they are dramatically different in their biochemical makeup and how they are loaded in the living horse. One site is impact-loaded intermittently, while the other is constantly loaded, but at a lower level.

By looking at the results of the biomechanical tests, researchers confirmed that a newborn foal’s cartilage is a “blank slate,” or biomechanically homogeneous (exhibiting the same properties over the entire joint surface). Harold Brommer, DVM, of Utrecht University in the Netherlands, explained, “At visual inspection, articular (joint surface) cartilage of the foal looks like normal cartilage of adult horses. However, the results of our study showed that the layer is much thicker and the biochemical make-up is quite different compared to the adult horse. This implies that the cartilage in the foal at birth has not the functional characteristics of the adult horse.”

“During early life, the functional characteristics have to be developed under the influence of loading, i.e. exercise, in order to get the functional quality that is needed to sustain loading without suffering injuries throughout life,” he added