Medial meniscus posterior root tears: A narrative review on the relationship and implications of meniscus extrusion

Medial meniscus extrusion, particularly in the setting of medial meniscus posterior root tears (MMPRTs), has become an area of interest in recent years due to the correlation between meniscus extrusion with inferior clinical outcomes, progression to osteoarthritis, and increased rate of conversion to total knee arthroplasty after MMPRT repair. This correlation led to the development of meniscus centralisations procedures that can be performed in addition to MMPRT repair and/or high tibial osteotomy. Although it was originally thought that medial meniscus extrusion was a consequence of MMPRTs, it has been reported that meniscus extrusion often precedes the development of MMPRTs, which suggests that there may be underlying meniscus pathology that predisposes to the development of both meniscus extrusion and MMPRTs. The purpose of this narrative review is to provide an overview of the anatomy, pathology, and surgical management of meniscus extrusion and MMPRTs, while identifying areas of future research to further elucidate the relationship meniscus extrusion and MMPRTs that may be necessary to improve outcomes after MMPRT repair. LEVEL OF EVIDENCE: Level V.