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In the present study, 119 hip joint samples and 126 knee joint samples from 32 dogs, aged between two month and 19 years have been examined in regard to osteoarthritic changes. The dogs, sent for necropsy into the institute of Veterinary-Pathology at the Freie Universität Berlin belonged to different medium- to big-sized breeds.Concerning patho-anatomical, radiological as well as patho-histological staging lead to the result which can be added to literature- that high grade 111 degeneration occurs more often in hip joints than in knee joints. At the sametime it was obvious that dogs with high grade patho-histological changes of knee joint always suffered from high grade hip degeneration. This result supports the opinion of theses authors who presume an initial hip degeneration with arising a wrong position of extremity with an increased mechanical load up on the lateral condyle of trochlea patellaris.The samples were taken from two different locations within one joint, exposed to different mechanical load. This procedure, which hasn"t been described in literature yet, showed that the continuing progression of hip degeneration seems mainly to depend on the functional stress. In case of differences in the staging of the two sites of excition, it had been found out for first time that the dorsolateral more loaded sample showed a higher degeneration degree than the ventromedial lesser functinally loaded sample. Similar new results occurred in the histological staging of knee joint. A comparison of lateral and medial condyle revealed a preceeded degeneration in the lateral condyle .The present study also searched for a further pathogenetic factor beside the functional pathogenesis of joint degeneration. Consequently it was inquired whether the expression of a heterotopic type of collagen with resulting arthritogenic characteristics might be considered.Therefore, following the patho-anatomical and histo-pathological classification 58 selected healthy and highly degenerated cartilage samples were examined immunohistochemically with regard to the antigenic determinants of collagen types, 1, 11, VI and procollagen 111.The immunohistochemical examinations confirm the common opinion of literature that the pressure resistent collagens 11 and VI belong to the orthotopic collagens occurring as well in the juvenile as in the adult healthy canine cartilage.The present study examined for the first time the heterotopic procollagen Ill in the canine hyaline cartilage. It has shown, that it does not occur in the juvenile cartilage of
joints but already in the early arthrotic cartilage before the ocurrence of histological changes. The heterotopical collagen 1 was detected, as described in literature, in the arthrotic canine cartilage. The amount increased with the ongoing of degeneration. In addition to descriptions in literature it could be shown in the early arthrotic cartilage and was missing in the juvenile cartilage.As these heterotopic collagens cannot withstand the arising physiological pressure, they may represent a determinative pathogenic factor in the ongoing of osteoarthritis. Heterotopic collagens represent arthritogenicauto-antigens so that also an autoimmune mediated arthritis might be considered in the pathogenesis of degenerative joint disease.