This article reviews the efficacy and safety of biological therapies—platelet-rich plasma (PRP), platelet-poor plasma (PPP), and autologous conditioned serum (ACS)—for treating knee osteoarthritis (KOA). PRP, rich in growth factors, shows mixed results, with its effects dependent on preparation methods. PPP offers a lower risk of inflammation, and ACS, high in anti-inflammatory cytokines, reduces KOA symptoms. The review highlights the need for standardized protocols and further research to establish the optimal use of these therapies, suggesting they may offer promising alternatives to traditional KOA treatments.