The aim of this study was to evaluate the effects of intra-articular application of hyaluronic acid injection on the cessation of cartilage degeneration in an experimental rabbit’s stifles osteoarthritis model induced by resection of the anterior cruciate ligament (ACL). Twenty clinically healthy rabbits weighing between 3150-4050 g, aged 7 months, were used in this study. Under general anesthesia osteoarthritis was induced on the right stifle joint of the rabbits. The ACL was resected and then the operation region was closed. Three months after the operation the animals were divided into two groups containing ten rabbits each. One group received a physiological saline injection, and the other received 1.0 ml of sodium hyaluronate (NaHa) dissolved in physiological saline that was injected into the right stifle joint given once a week three times. All subjects were sacrificed at the end of the postoperative 6th months. For the macroscopic examination, the cartilage surfaces of the loaded parts of the femur and tibia were grossly evaluated. The cartilage degeneration was increased in severity, and there was even the abrasion of the total cartilage layer in some cases. On the other hand, the degeneration in the NaHa-applied group was relatively minor, and stifles were smooth, white, and glistening. The joints subjected to NaHa treatment showed less granulation tissue than the other group did. According to light microscopic evaluation, cartilage exhibited an irregular surface and loss of normal cellularity in the saline group. Surface irregularity had nearly normal tidemark integrity and cellularity after treatment with NaHa. According to the electron microscopic evaluation, cartilage surfaces showed irregularities, loss of extracellular matrix metachromasia, and a decreased number of chondrocytes within their lacunae at several locations in saline-treated group. These disturbances were less prominent in the NaHa group compared to the saline group. Although degenerating chondroblasts and chondrocytes with their picnotic nuclei were apparent in both groups, the NaHa group had a normal chondral matrix area with healthy chondrocytes within their lacunae forming isogenous groups. As a result, it was concluded that using hyaluronic acid in the treatment of osteoarthritis is beneficial.