Veterinary specialists are actively studying the problem of osteoarthritis in animals (horses, dogs, cats, rabbits) and methods of overcoming it. At present, there are classical treatment regimens that give positive results, and the use of platelet-rich plasma (PRP) is being actively introduced into veterinary practice. In this regard, the studies described in this article were aimed at applying the effectiveness and evaluating changes in animals with experimental knee osteoarthritis of non-steroidal anti-inflammatory drugs in combination with chondroitin and glucosamine (classical treatment regimen) and platelet-rich plasma. The material of the study was synovial fluid obtained from animals with experimentally formed osteoarthritis of the knee joint on days 7, 14, 21 and 28 after the start of treatment using two different methods. In the animals of the experimental group (classical treatment regimen), on the 7th day, a decrease in the number of neutrophils by 31%, eosinophils by 12.5%, the number of lymphocytes increased by 31.3%, and macrophages decreased by 7% was observed. The number of lymphocytes increased by 7.3% compared to the baseline. On the 14th day, the number of neutrophils decreased by 61.5%, eosinophils by 45%, macrophages by 37.9%, and the number of lymphocytes increased by 4.5% compared to the 7th day. On the 21st day, the number of neutrophils decreased by 46.7%, eosinophils by 39.4%, macrophages by 51%, and the number of lymphocytes increased by 10.9% compared to the 14th day. On the 28th day, single neutrophils, eosinophils, and macrophages were observed in the synovial fluid samples, which corresponds to the physiological norm of synovial fluid composition. At the same time, the number of lymphocytes increased by 14.9% compared to the values of 21 days, but remained within the reference values. In animals treated with platelet-rich plasma on day 7, the number of neutrophils decreased by 54.7%, eosinophils by 33.7%, macrophages by 34% compared to the baseline, and the number of lymphocytes increased by 34% compared to the baseline. On the 14th day of the experiment, the number of neutrophils decreased by 60.5%, eosinophils by 37%, macrophages by 44.6%, and the number of lymphocytes increased by 10.5% compared to the 7th day, but were within the range of acceptable reference values. On day 21, single neutrophils, eosinophils, and macrophages were observed in the synovial fluid samples of animals of this group. It should be noted that the number of lymphocytes increased by 9.8 % compared to the values of day 14, which corresponds to the physiological norm of synovial fluid composition. On the 28th day of the experiment, single neutrophils and eosinophils were observed in the synovial fluid. At the same time, the number of lymphocytes increased by 19.5 % compared to day 21, which corresponds to the physiological norm of synovial fluid composition. The scientific material of experimental studies is of practical value for the use of platelet-rich plasma in the treatment of animals with osteoarthritis.
