Softening and erosion of cartilage, the characteristic early lesions of osteoarthritis, occur in sites of decreased chondroitin sulfate concentration. The role of aging and the specific biochemical events that produce this alteration in glycosaminoglycan composition have been under study in several laboratories. Collins and McElligott found increased radiosulfate fixation in these lesions compared with normal articular cartilage from the same individuals, suggesting increased synthesis of polysaccharide (1). These observations indicated an increased turnover of chondroitin sulfate in osteoarthritic cartilage lesions, and attention has become focused on the mechanism responsible for breakdown of this glycosaminoglycan.As reported previously (2), when the cartilage proteinpolysaccharide complex was extracted from human articular cartilage obtained at autopsy, a decrease in the concentration of chondroitin sulfate but not protein was found in the areas of erosion. This observation pointed to a specific breakdown of the glycosaminoglycan, since proteolysis might be expected to cause removal of both components such as occurs after papain injection into rabbits (3). An enzyme resembling testicular hyaluronidase could be responsible, but reports of the presence of hyaluronidase in tissues other than testis were unconvincing or unconfirmed. A reevaluation of the tissue distribution of this enzyme resulted in the finding of an enzyme with most of the characteristics of testicular hyaluronidase in

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