Medial Meniscal Extrusion: A Narrative Review of Etiology, Diagnosis, and Therapeutic Strategies.

Objective: To comprehensively review recent developments in the etiology, imaging diagnosis, and treatment strategies for medial meniscal extrusion, highlighting biomechanical considerations and individualized therapeutic approaches. Methods: We performed a narrative review of English-language clinical, imaging, and biomechanical studies by searching PubMed, Web of Science, and Embase from database inception to June 30, 2024, using terms related to meniscal extrusion, meniscal root tears, meniscotibial ligament injury, osteoarthritis, and corrective osteotomy, and we also screened reference lists of relevant reviews. Studies were included if they explicitly evaluated medial meniscal extrusion and reported quantitative extrusion assessment and/or its determinants, diagnostic performance, or treatment-related changes; we excluded studies not focused on medial extrusion, non-original articles without analyzable data, and reports lacking quantifiable extrusion outcomes. Results: Eighty-five studies were included for qualitative synthesis. Current evidence indicates that medial meniscal extrusion most commonly arises from posterior root tears and degenerative tears that disrupt hoop tension, and is further amplified by meniscotibial ligament insufficiency, varus malalignment, increased body mass index, osteophytes, and subchondral insufficiency fracture, forming a self-reinforcing pathway of extrusion, compartment overload, cartilage loss, and subchondral bone changes. MRI remains the reference standard for static assessment, whereas ultrasound and weight-bearing protocols better capture load-dependent displacement; however, measurement planes, anatomical landmarks, and thresholds vary, limiting cross-study comparability. Across treatment studies, reported strategies ranged from structured nonoperative care to root repair, meniscal centralization, and high tibial osteotomy. In appropriately selected knees, studies evaluating combined biomechanical correction and meniscal stabilization more consistently reported measurable reductions in extrusion than isolated procedures, although outcome definitions and follow-up durations were heterogeneous. Conclusion: Medial meniscal extrusion is best understood as a mechano-structural failure state rather than an isolated imaging sign. Standardized measurement strategies and prospective comparative studies are needed to define actionable thresholds and refine patient-specific treatment pathways.