A standardized pharmacological model of biochemically induced osteoarthritis in the knee joint of laboratory animals was used for the study of a possible antidegenerative effect of ademetionine (S-adenosyl-methionine, active substance of Gumbaral) in-vivo. Four days after the initial induction of osteoarthritis by 2 intraarticular injections of 0.6 mg sodium iodoacetate into the left knee joint of adult hens, the therapy started with once-weekly intraarticular doses of 0.5 mg, 1.0 mg and 2.0 mg ademetionine over a period of 14 weeks. Quantitative monitoring of the intensity and progression of osteoarthritis was performed every 2 weeks by joint space measurements, topographic-radiological evaluations, and by a macroscopic post-mortem assessment of the joint cartilage and bone. These objective analytical parameters clearly demonstrated that weekly intraarticular doses of 1.0 mg ademetionine significantly reduced the intensity of degenerative processes compared to the placebo (saline) treated joints. The antidegenerative effect of doses of 0.5 mg or 2.0 mg ademetionine were less pronounced and of no statistical significance. Our findings indicate an interesting therapeutic potency of ademetionine in experimental osteoarthritis and confirm the positive clinical observations as well as in-vitro results with this new drug by other researchers.