Biomechanical properties of third carpal articular cartilage in exercised and nonexercised horses

The relevance of site and exercise on the biomechanical properties of the articular cartilage from the equine third carpal bone were assessed by creep indentation testing. Six horses were exercised for 30 minutes three times weekly. Another six horses were housed in box stalls and were not exercised. At the conclusion of the study, one third carpal bone from each horse was harvested and the KLM biphasic material properties of cartilage were determined at 12 sites. There was a significant (p < 0.01) effect of site but not exercise on the cartilage aggregate modulus, which was significantly lower for sites on the dorsal aspect of the radial facet and for all sites on the intermediate facet as compared with sites on the palmar aspect of the radial facet of the third carpal bone. Exercise significantly increased the permeability constant at all sites when compared with the nonexercised group, but there was no difference between sites within groups. Exercise also significantly increased Poisson's ratio, but only at sites located on the palmar aspect of the radial facet. In general, both site and exercise influence the biomechanical behavior of third carpal articular cartilage. Inherent differences in cartilage biomechanical properties within a joint correlate with the location specificity of cartilaginous lesions in the equine midcarpal joint.