Injections of platelet-rich plasma are considered to be a promising treatment. Medicines acting on the subchondral bone can improve tissue's structure and slow down destruction of the articular cartilage. This study aimed to analyze the results of intraarticular and intraosseous administration of platelet-rich plasma (PRP) in gonarthrosis cases. One hundred and eighty-seven participants (gonarthrosis stages 1 through 3) were divided into three groups. Group 1 (treatment group) received intraarticular PRP injections, group 2 (comparison group) — intraosseous PRP injections. For assessment purposes, we used the SF-36 survey and visual analog scale. Three months after the treatment, initial pain level decreased in both groups 1 and 2. In group 1, the prevalence of synovitis went down after 3 months, in group 2 — after 6 months (21.9 and 31.3%, respectively; p < 0.05). Six months after the treatment, soft tissue swelling around the joint was registered less often in groups 1 and 2 (8.2 and 8.3%, respectively). As for the physical component of the quality of life, it improved in group 1 after 3 months (70.40%), in group 2 — after 6 months (69.80%); as for the mental component, the dynamics was acknowledged positive 3 months after the treatment in groups 1 and 2 (64.30 and 65.10%, respectively), and 6 months after the treatment (65.10 and 66.40%, respectively). Thus, administration of PRP in gonarthrosis cases attenuate pain and improves the quality of life. In terms of alleviation of the clinical symptoms and improvement of the physical component of patients' lives, intraosseous PRP injections performed significantly better.