Review of Meniscus Root Tears
Introduction
The meniscus plays a role in the distribution of tibiofemoral forces, joint congruency, and shock absorption (6, 7). The medial and lateral menisci are suspended to the tibia via ligament-like structures known collectively as the meniscal roots (1). The meniscus roots will anchor the anterior and posterior horn of the medial and lateral menisci to the tibia (3). There are other ligamentous supports of the meniscus that go beyond the scope of this review including the menisotibial ligaments, popliteomeniscal fascicles, meniscofibular ligaments, and meniscofemoral ligaments (3).
The main goal of the meniscus root is to prevent meniscus extrusion so that the meniscus can continue to decrease load to the articular cartilage (1). When an axial load acts upon the joint, it directs forces towards the outside of the joint and then there is a counter tensile stress (AKA hoop stress) by the meniscus to resist this force and distribute forces evenly across the joint surface (8). The loss of hoop stress of the meniscus can lead to the development of osteoarthritis (1).
Injuries to the meniscus root can be acute or chronic. Root tears have been identified in 4.3% of all arthroscopic knee surgeries and over half have been of the posterior meniscus root (6). Acute medial meniscus root tears are seen in young athletes with a hyperextension mechanism (4). Acute on chronic medial meniscus root tears are found in moderate osteoarthritis (4).
The anterior horn of the medial meniscus root inserts on the intercondylar crest and has a larger area of insertion than the anterior horn of the lateral meniscus (6). As a result of the larger area of insertion and thicker root, the anterior roots can withstand greater forces than the posterior roots (6).
One of the most common roots injured is the posterior medial meniscus root ligament (PMMRL) (1). The insertion of the PMMRL is between the posterior cruciate ligament and the posterior root of the lateral meniscus (1). Injures to the PMMRL are associated with higher rates of total knee arthroplasty (4).
Imaging of the Posterior Medial Meniscus Root (1)
Diagnosis
There is no physical exam test that accurately identified meniscus root tears (6). The typical mechanism suggestive of a meniscus root injury is pain with deep knee flexion or pain after an acute twisting episode (6). A 3T MRI has a 100% positive predictive value for a medial root tear (6). On MRI, signs of a root tear are 3mm of meniscus extrusion, subchondral marrow edema, and a “ghost” sign (6). The ghost sign is the sudden absence of the meniscus between sagittal plane images (6). More than 3mm of meniscus extrusion seen on an MRI is commonly found in patients with moderate to severe medial compartment articular cartilage loss (7).
Complete tear of the Posterior Medial Meniscus Root (1)
Treatment
There is emerging evidence regarding the surgical repair of meniscal root tears. Early evidence shows a slowing of the progression of OA with meniscus root repair (6). Further evidence is needed into different techniques for meniscus root repairs.
Conclusion
The meniscus roots play an important role in maintaining joint congruency and proper distribution of forces across the meniscus. Tears of the meniscus roots can lead to increased articular cartilage degeneration and early knee OA. As a result, prompt diagnosis with MRI may lead to surgical treatment in select patients.
By Gregory Rubin, DO
rubinsportsmed.com
– Read More @ Wiki Sports Medicine: https://wikism.org/Meniscal_Tears
References
1) Choi, Ja-Young, et al. “Posterior Medial Meniscus Root Ligament Lesions: MRI Classification and Associated Findings.” AJR. American Journal of Roentgenology, vol. 203, no. 6, Dec. 2014, pp. 1286–92. PubMed, https://doi.org/10.2214/AJR.14.12559.
2) Kim, Young Mo, and Yong-Bum Joo. “Anteromedial Meniscofemoral Ligament of the Anterior Horn of the Medial Meniscus: Clinical, Magnetic Resonance Imaging, and Arthroscopic Features.” Arthroscopy: The Journal of Arthroscopic & Related Surgery: Official Publication of the Arthroscopy Association of North America and the International Arthroscopy Association, vol. 34, no. 5, May 2018, pp. 1590–600. PubMed, https://doi.org/10.1016/j.arthro.2017.12.010.
3) Chahla, Jorge. “Meniscal Pathology: Meniscus Anatomy.” Evidence-Based Management of Complex Knee Injuries, Elsevier, pp. 151–75.
4) Dragoo, Jason L., et al. “Outcomes of Arthroscopic All-Inside Repair Versus Observation in Older Patients With Meniscus Root Tears.” The American Journal of Sports Medicine, vol. 48, no. 5, Apr. 2020, pp. 1127–33. PubMed, https://doi.org/10.1177/0363546520909828.
5) Faucett, Scott C., et al. “Meniscus Root Repair vs Meniscectomy or Nonoperative Management to Prevent Knee Osteoarthritis After Medial Meniscus Root Tears: Clinical and Economic Effectiveness.” The American Journal of Sports Medicine, vol. 47, no. 3, Mar. 2019, pp. 762–69. PubMed, https://doi.org/10.1177/0363546518755754.
6) Kennedy, Mitchell I., et al. “Injury of the Meniscus Root.” Clinics in Sports Medicine, vol. 39, no. 1, Jan. 2020, pp. 57–68. PubMed, https://doi.org/10.1016/j.csm.2019.08.009.
7) Lerer, D. B., et al. “The Role of Meniscal Root Pathology and Radial Meniscal Tear in Medial Meniscal Extrusion.” Skeletal Radiology, vol. 33, no. 10, Oct. 2004, pp. 569–74. PubMed, https://doi.org/10.1007/s00256-004-0761-2.
8) Lee, So Yeon, et al. “Radial Tear of the Medial Meniscal Root: Reliability and Accuracy of MRI for Diagnosis.” AJR. American Journal of Roentgenology, vol. 191, no. 1, July 2008, pp. 81–85. PubMed, https://doi.org/10.2214/AJR.07.2945.
9) Bhatia, Sanjeev, et al. “Meniscal Root Tears: Significance, Diagnosis, and Treatment.” The American Journal of Sports Medicine, vol. 42, no. 12, Dec. 2014, pp. 3016–30. PubMed, https://doi.org/10.1177/0363546514524162.
