"Joint failure" may be the result of different pathological conditions. While in some arthropathies initial changes prior to secondary cartilage destruction may be observed morphologically, the early changes in "mechanically induced" osteoarthrosis are not well known. In the present paper the ultrastructural events, eventually leading to osteoarthrotic cartilage destruction are presented. From the morphological changes it is assumed that the primary lesion leading to cartilage destruction may be seen in the loss of the granular surface microstructures of cartilage that may be followed by an increased hydration and thereafter chondrocytic death with destruction of cartilaginous matrix.