Objective:To evaluate the effect of intra-articular injection of different concentrations of ozonated water on articular cartilage of rabbits with osteoarthritis (OA).Methods:Twenty-four clean-grade New Zealand white rabbits of both sexes, weighing 2.0-3.0 kg, aged 6 months, were divided into 4 groups ( n=6 each) using a random number table method: control group (group C), OA group, low concentration ozonated water group (L group) and high concentration ozonated water group (H group). The OA model was established by intra-articular injection of papain.At 2 weeks after the model was successfully established, 10.0 and 20.0 μg/ml ozonated water 1.0 ml was injected into the knee joint of rabbits in L and H groups, respectively, and 0.9% sodium chloride solution 1.0 ml was injected once a week, 3 times in total in OA group.At 1 week after the last injection, the cartilage tissue of the knee joint was removed and stained with toluidine blue for evaluation of Mankin score (under light microscope). The activity of caspase-3 in chondrocyte was detected by enzyme-linked immunosorbent assay. Results:Compared with group C, the Mankin score and caspase-3 activity were significantly increased in the other 3 groups ( P<0.05). Compared with group OA, the Mankin score and caspase-3 activity were significantly decreased in group L and group H ( P<0.05). Compared with group L, the Mankin score was significantly increased, and the activity of caspase-3 was decreased in group H ( P<0.05). Conclusion:Injecting ozonated water 10.0 μg/ml and 20.0 μg/ml into the knee joint cavity both can inhibit the apoptosis in chondrocytes and reduce the damage to articular cartilage, however, high concentration of ozonated water can cause the denaturation of the articular cartilage matrix in rabbits with OA.