The present study has focused on the cartilage-bone interrelationships in the progression of osteoarthrosis in human knees. Eleven tibial condyles with osteoarthrosis were analyzed by histology and bonemorphometry. The data were evaluated according to the grade of joint cartilage degeneration in distinct areas of the tibial condyle. The bone morphometric data were also analyzed by the depth of subchondral bone. A parallel relationship between the bone volume/bone formation activity and the Mankin's grade of cartilage degeneration was observed in both medial and lateral condyles. In the lateral condyle, there was correlation among progression of cartilage degeneration and trabecular and osteoid thickness and bone formation activity. Osteoblasts and osteoclasts were most abundant in the external areas of the medial condyles. Bone resorption activity in the medial condyle was found only in the external and intermediate areas, but it was extremely low in all areas of the lateral condyle. The values of bone volume in relation to depth were highest in the superficial layer with a decrease as the depth increased in both condyles. The bone formation activity was high in the superficial layer of the lateral condyle, whereas in the medial condyle, it was high in the layer between 500 and 1,500 microns of depth. The bone volume and bone formation activity were higher in all layers of the medial condyle in comparison with the lateral condyle. The bone resorption activity was low in the superficial layer of the medial condyle as compared with deeper layers. These results suggested that the joint cartilage degeneration is influenced by the remodeling of the underlying subchondral bone.