Meniscus extrusion after a medial meniscus root repair: Where we are and how can we solve it?

Medial meniscus extrusion (MME) is the displacement of the meniscus beyond the edge of the medial tibial plateau. Proposed etiologies for MME include biologic degeneration of meniscal tissue, the result of a medial meniscus posterior root tear (MMPRT), and the failure of the meniscotibial ligament. Standard MMPRT repairs do not address this MME, as it often persists or worsens postoperatively, even with successful root healing. New techniques, such as centralization sutures, have been developed to supplement the standard MMPRT repair technique. Systematic reviews and randomized controlled trials confirm that the addition of a centralization suture significantly reduces MME, improves joint contact pressures, and enhances patient-reported outcomes. Even though postoperative extrusion still exists after centralization suture use, likely due to the degenerative nature of the meniscus, this represents a shift towards improved knee joint preservation. Continuing progress in this field requires standardization of measurement and diagnosis, establishing the minimal clinically important difference of postoperative extrusion for a successful MMPRT repair, and long-term clinical evidence. This narrative review will explore current understanding of MME, current treatment options, and topics to guide future research.