Release of Nano- and Microplastics from Knee Prostheses: A Review of the Emerging Risks and Biomedical Implications

Contemporary knee prostheses rely predominantly on a metal–polyethylene bearing couple, which—despite substantial advances in material engineering—continues to generate polymeric wear particles over time. While the local biological effects of polyethylene debris, such as inflammation and osteolysis, are well-characterised, their potential systemic implications remain insufficiently explored. In this review, we synthesise multidisciplinary evidence to evaluate the generation, biological behaviour, and systemic dissemination of polyethylene-derived nano- and microplastics (NMPs) released from knee prostheses. We also contextualise prosthetic wear within the broader toxicological framework of NMP exposure, highlighting translocation pathways, interactions with immune and metabolic systems, and potential multi-organ effects reported in recent experimental and clinical studies. Current findings suggest that prosthetic wear may represent an under-recognised internal source of NMP exposure, with possible implications for long-term patient health. A clearer understanding of the systemic behaviour of prosthetic-derived NMPs is essential to guide future biomonitoring studies, improve prosthetic materials, and support the development of safer, more biocompatible implant designs.