Hyaluronan is known to play an important role in the healing of degenerative osteoarthritis. But there is no clear consensus how it effects on osteoarthritis compare to cortisone. The purpose of the research was to determine the comparative effects of hyaluronan and cortisone on the healing of degenerative osteoarthritis. A rabbit model used in which & degenerative osteoarthritis were created in the articular cartilage by the inoculation of Staphylococcus Aureus (S. Aureus). The rabbits divided into two groups namely injected with hyaluronan (group A) and cortisone (group B) at days 20, 23 and 26. After hyaluronan and cortisone injections for treatment of osteoarthritis at day of 25 and 35 six rabbits (each of three injected with hyaluronan and cortisone) and at day 50 (six of injected with hyaluronan and five of cortisone) were sacrified. In biopsies obtained from these knees both articular cartilage degeneration and inflammation around the joint were examined by light microscopy. It was seen that the histopathologic findings were consistent with active chronic inflammation at day 10, followed by chronic inflammation. At day 5 of treatment the degeneration decreased (60%) in group A, and clinical findings disappeared after day 9 of treatment. At day 15 of hyaluronan treatment the degeneration degree regressed and at day 30 absolutely healed (all except :)ne). In group B, at day 5 of treatment, the clinical findings disappeared and the healing rate was 72%. At day 15 of cortisone treatment, the degeneration slightly increased and at day 30 the degeneration degree increased more than that day of 15. The results showed that cortisone is effective in the treatment of cartilage degeneration and inflammation early in the course of the septic arthritis whereas the therapeutic effect of hyaluronan is higher late in the course of the disease. Further studies are required in order to understand the effectiveness of the combined or consecutive use of these drugs in degenerative osteoarthritis.