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The relationship between early degeneration of articular cartilage and the energyabsorbing abilities of its subchondral bony bed was studied in specimens obtained at autopsy from the knees of 43 male patients. Subchondral bone plugs from patients whose cartilage had only mild mucopolysaccharide loss absorbed relatively less energy on impact than the normals. There was no apparent difference in energy absorption among the bone plugs of the normal, the moderate, and the markedly altered cartilage groups. These changes were not age related.The etiology of degenerative joint disease has eluded investigators for centuries. Contrary to classical teachings, our work on the ability of whole joints to attenuate the peak force occurring during rapidly applied loading has suggested that bone and soft tissues play a larger part than synovial fluid and cartilage in attenuating such forces (1 itive joint disease is related to the joint's inability to handle large loads, alterations in bone could significantly affect the pressures exerted on articular cartilage. The primary change in degenerative joint disease could be, therefore, in the bone. To test this hypothesis, the mechanical properties of cancellous bone from a small group of patients with varying degrees of degenerative joint disease were studied. MATERIALS AND METHODSSubchondral bone plugs, '/4 inch in diameter, were obtained at autopsy from identical spots on the weight-bearing portion of the medial femoral condyle of the right knee of 43 male patients. These patients had no history of joint disease, were from 28 to 92 years old and weighed from 108 to 184 lb. Adjacent plugs were taken for histologic examination. They were immediately fixed in a$-tated Bouin's solution for 12 hr at 4 O C, then decalcified in the cold in neutral buffered EDTA and stained with safranin red-0, a stain specific for mucopolysaccharides (2). The slides were counterstained with methyl green.The plugs for mechanical testing were immediately frozen (unfixed), stored and thawed just 400