Articular cartilage from the knees of 4 dogs whose ipsilateral paws had been transected 6 weeks earlier (knee,,,,,), and from their contralateral knees (knee,,), was examined. Knee,,,,, did not bear weight as a result of the surgical procedure but active motion of the joint, determined with an angular displacement monitor during walking, was comparable to that of knee,,.. In comparison to knee,, cartilage, knee,,,, samples showed decreases in thickness, Safranin-0 staining of the matrix, and uronic acid content (mean, 24.4%), and increase in water content (mean, 5.9%). Incorporation of into proteoglycans was 34-67% less in knee,,,,, than in knee,,, cartilage. Proteoglycan (PC) aggregation in knee,, cartilage was normal, whereas in knee,,... cartilage the bulk of the proteoglycans, and also those that had been newly synthesized ('5S-proteoglycans), did not exist in aggregates. This defect in aggregation was due, at least in part, to an abnormality in the hyaluronatebinding region of the core protein of the proteoglycans, since they did not interact in vitro with hyaluronic acid These changes are essentially identical to those shown

In osteoarthritis a net increase in proteoglycan synthesis has been noted until the disease is far advanced and presumably reflects an attempt by the chondrocyte to repair the defect in the cartilage matrix. Because salicylates are the agents most commonly employed in treatment of osteoarthritis and because we recently showed that 10−3M sodium salicylate (i.e., approximately 20 mg%) suppresses proteoglycan synthesis in normal canine knee cartilage in vitro, we have studied the effects of this compound on osteoarthritic knee cartilage from dogs whose anterior cruciate ligament had been transected 9 weeks previously. The data indicated that the augmented synthesis of glycosaminoglycans in the degenerating cartilage was suppressed to a much greater degree by 10−3M sodium salicylate than the lower level of glycosaminoglycan synthesis in control cartilage from the contralateral knee of the same animal. Uptake of 14C‐acetylsalicylic acid was increased about 35% in osteoarthritic cartilage, suggesting that the drug permeated it more readily than normal cartilage. The salicylate‐induced suppression of proteoglycan synthesis in the osteoarthritic cartilage was not accompanied by reversal of the defect in proteoglycan aggregation or by improvement in the (presumed) defect in proteoglycan‐collagen interaction in the matrix, as reflected by the abnormally high proportion of 35S‐proteoglycans present in the culture medium.

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