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Background
Meniscal roots serve to anchor the fibrocartilaginous menisci onto the tibia, prevents the meniscus from being extruded, and allows the meniscus to generate hoop stress. Meniscal roots enables the menisci to effectively transfer the load from the femur to the tibia while protecting the articular cartilage from excessive load. Complete meniscal root tear results in loss of hoop stress, which is nearly functionally identical to that of total meniscectomy and a critical risk factor of early osteoarthritis. Tears of the posterior meniscal root can be easily missed because of inconsistent clinical symptoms and can be overlooked without thorough arthroscopic examination.

Educational Goals / Teaching Points
Understand the anatomy of the meniscal roots, imaging features, clinical relevance, and associations of meniscal root tears. Be familiar with the basic concepts of meniscal root repair

Key Anatomic/Physiologic Issues and Imaging Findings/Techniques
Three anatomical segments of the meniscal root, entheseal, midsubstance, junction to meniscus. In contrast to the anterior root attachments, posterior root attachments are relatively complex. Meniscal root tears are defined as tears within 1 cm from its insertion. Most of the root tears involve the posterior medial meniscus root and are the result of degenerative meniscal disease and frequently found in middle-aged females. Posterior lateral meniscus root tears are usually traumatic and have been reported in 7–12% of patients with an ACL tear. Meniscal root serves as a secondary stabilizer of the knee joint and resists both rotational and translational stress. Following root tears, the medial meniscus often extrudes on axial loading, subjecting the articular surfaces to increased stress, chondral loss and osteoarthritis. Extrusion of the lateral meniscus in the case of a root tear is observed infrequently. Clinical impact of a lateral meniscus posterior root tear is likely influenced by the integrity of the mensicofemoral ligaments (MFLs). Coronal T2-weighted sequence is the most accurate imaging plane to diagnose root tears. Preoperative diagnosis is the key as many of the root tears are not recognizable on arthroscopy. Avulsion of the anterior root is exceedingly rare. Both gray signal in the posterior root medial meniscus and focal subcortical marrow edema deep to the root attachment is predictive of ensuing root tear when imaged within a time interval of 13.5 months. Close imaging follow-up for the “root at risk” may prove useful for identifying progression to complete tear in a timely fashion, and allow surgical treatment before cartilage damage has developed. Surgical reattachment and meniscal preservation methods are currently treatment of choice.

Conclusion
Posterior medial meniscus root tears are the most common root tears and have a high association with degenerative joint disease, chondral defect of medial femoral condyle and medial meniscal extrusion. Posterior lateral meniscal root tears have a high association with ACL tears. Assessing the integrity of MFLs determine the biomechanical consequences of the tear. Reporting the anatomic site of root tear may aid surgical technique planning.