The aim of this study was to evaluate the treatment of osteoarthritis (OA) in dogs with intra-articular injection of an (autologous platelet-rich plasma (PRP), Mesenchymal stem cells (MSCs), bio-physically activated platelet-rich plasma (B-PRP/plasma-poor platelets-PPP) and their combinations and to determine the changes in the levels of synovial fluid samples (inflammatory mediator, proteases (MMP-2 and MMP-9) and collagenase enzymes (MMP-1, MMP-8 and MMP-13) obtained from the joints. Total of 36 different breeds, sex, age and weight of dogs with osteoarthritis were used as the material. The groups were divided as Group I (PRP), Group II (MSCs), Group III (PRP + MSCs), Group IV (B-PRP), Group V (B-PRP + MSCs) and group VI (saline control). Only single injection was given. Metalloproteinases were measured by using the ELISA in preoperative and postoperative treatment of 0, 15th, 30th, 60th, and 90th days in synovial fluid samples. Clinical and radiographic examinations were performed on the 0, 15th, 30th, 60th, and 90th days. The results obtained from the PRP + MSCs combination group were more successful. It was also noted that successful results could be obtained with PRP alone or in combination with stem cells, especially if repeated intraarticular injections are required for osteoarthritis. New studies are needed to understand the effectiveness of B-PRP. Only B-PRP or stem cell combination was effective on many enzymes, but varying results were obtained with each case.