Abstract
1. The venographic findings in clinical primary osteoarthritis are described. 2. Experimental venous engorgement, of the knee joint and of healing fibular fractures, results in accelerated bone formation and disturbed cartilage formation. 3. Changes in pH, ppCO2, and PPO2 are indicated as the chemical means by which chondrogenesis and osteogenesis can be altered. 4. It is suggested that chronic venous stress in joints is a causal factor in primary osteoarthritis.