Changes in the spatial arrangement of the trabeculae (rather than the gross density of the bone) are shown to correlate with the observed increase in subchondral bone stiffening associated with loss of cartilage mucopolysaccharide. In fifteen cadavera, with no histories of degenerative joint disease and exhibiting no gross bone and cartilage changes indicative of osteoarthritis, the stiffening of 38 per cent from a normal to an early arthritic condition was accompanied by a trabecular contiguity change from 0.7 to 0.8. Since the limits on the contiguity ratio in trabecular bone are one-half and one, and the experimentally observed range is 0.6 to 0.9, this increase in contiguity ratio is quite striking.