The influence of strenuous exercise on collagen characteristics of articular cartilage in Thoroughbreds age 2 years

In order to assess the influence of strenuous exercise on collagen characte ristics of articular cartilage, the response of the collagen network was st udied in seven 2-year-old Thoroughbreds subjected to strenuous exercise com pared to 7 nontrained individuals. After 13 weeks, the animals were subject ed to euthanasia, fetlock joints of the forelimbs were scored macroscopical ly after Indian Ink staining, and articular cartilage from different locati ons of the articular surface of the proximal first phalanx was sampled and analysed for water content, collagen content, hydroxylysine content and amo unt of hydroxylysylpyridinoline (HP) crosslinks. Gross lesions were signifi cantly more severe in the exercised than in the nonexercised group. In the control animals, the characteristic site-specific differences in collagen p arameters were found as described earlier, but in the strenuously exercised animals this physiological biochemical heterogeneity had disappeared. In t he exercised animals, an increase in water content and a sharp decrease in HP crosslinking was found that was correlated with the presence of wear lin es. It is concluded that the strenuous exercise provoked significant altera tions in the characteristics of the collagen network of the articular carti lage of the fetlock joint which were suggestive of microdamage and loosenin g of the collagen network. The collagen component of cartilage, in contrast to the proteoglycan component, is known to have a very limited capacity fo r repair and remodelling due to an extremely low turnover rate. Therefore, alterations within the articular collagen network might be expected to play an important role in the pathophysiology of degenerative joint disorders.