The meniscus is the only tissue in the joint that is not covered by synovial membrane, with a thick circumferential edge and a thin inner edge, and its coronal surface has a triangular structure. The medial meniscus is larger, “C”-shaped, narrow anteriorly and widely posteriorly, and the edges are tightly attached to the joint capsule and the tibial collateral ligament. Care should be taken to protect the medial collateral ligament when cleaning the medial meniscus during TKA. The lateral meniscus is smaller, a 2 / 3 annulus with comparable size of anterior and posterior angles, separated by muscle keys and row of collateral ligaments, so the lateral meniscus has more flexibility than the medial meniscus. The functions of the meniscus are load transfer, stability maintenance, lubrication, and shock mitigation.