The study compared the effectiveness of sequential and single intra-articular injections of platelet-rich plasma (PRP) in the treatment of early and intermediate stage osteoarthritis of the knee in 94 patients. After 6 months of treatment, there was a significant improvement in the levels of inflammatory markers (IL-1β, IL-6, TNF-α) and enzymes in the synovial fluid (MMP-3, TIMP-1) in both groups. The group with sequential PRP injections showed a more significant reduction in inflammatory markers and better TIMP-1 values compared to the single injection group. Both groups experienced improvements in pain scores (VAS) and knee function (WOMAC, Lysholm) after 1, 3 and 6 months. After 6 months, the sequential injection group had lower pain scores and better functional scores than the single injection group. Complications did not occur significantly differently between groups, and all cases resolved after treatment. Thus, the sequential application of PRP brings a more permanent and significant clinical benefit in the treatment of early and middle stage osteoarthritis of the knee.