The roots extend into the bone of the tibia and anchor the horns of the meniscus.
A root tear separates the root from the rest of the meniscus, and makes the meniscus incompetent.
Function of the meniscal root
A key function of the meniscus is the conversion of vertical load into circumferential load, so that forces are displaced to the outer edges of the meniscus rather than right through the cartilage of the two bones where they make contact. The integrity of the root is essential and a tear here is a potential disaster because if left unrepaired the situation is equivalent to a meniscectomy. However, surgeons have only understood this fairly recently and repair of a meniscus root tear is not a skill yet acquired by most knee surgeons.
Anatomy of the anterior root attachments of the medial and lateral menisci: a quantitative analysis. LaPrade CM, Ellman MB, Rasmussen MT, James EW, Wijdicks CA, Engebretsen L, LaPrade RF. Am J Sports Med. 2014 Oct;42(10):2386-92. doi: 10.1177/0363546514544678. Epub 2014 Aug 8.
Consequences of tibial tunnel reaming on the meniscal roots during cruciate ligament reconstruction in a cadaveric model, Part 1: The anterior cruciate ligament. LaPrade CM, Smith SD, Rasmussen MT, Hamming MG, Wijdicks CA, Engebretsen L, Feagin JA, LaPrade RF. Am J Sports Med. 2015 Jan;43(1):200-6. doi: 10.1177/0363546514554769. Epub 2014 Oct 31.
Understanding posterior meniscal roots lesions: from basic science to treatment. Cruz RS, Ferrari MB, Metsavaht L and LaPrade RF. Revista Brasileira de Ortopedia (English Edition), Volume 52, Issue 4, June–July 2017, 463-472.