The meniscus is the fibrocartilage inside the knee joint, the two pads inside the knee (one on the inside and one on the outside), and is called the meniscus because it is half-moon shaped. The one on the inside of the knee is called the medial meniscus, which is C-shaped, and the one on the outside of the knee is called the lateral meniscus, which is O-shaped. The meniscus fills the space between the femoral and tibial condyles and has the function of absorbing shock, cushioning pressure, enhancing the stability of the knee joint, preventing knee injury and slowing down the aging of the knee joint. Meniscal injuries are most often caused by torsional forces. When a person flexes the knee joint and the corresponding foot is fixed while twisting the knee joint, that means an acute meniscal tear may occur. As the knee gradually degenerates with age, the meniscus may rupture after prolonged wear and tear, even without a clear history of trauma. If the ruptured meniscus is stuck between the knee joints, it can cause impaired knee motion, affecting flexion and extension, and creating “interlock”. Since the meniscus itself lacks blood supply, its nutrition mainly comes from synovial fluid, and only the marginal part connected to the joint capsule can get some blood supply from the synovial membrane. Therefore, except for the marginal part, which may be repaired by itself, in most cases, meniscal rupture cannot be repaired by itself and requires arthroscopic surgery for meniscal suturing or shaping.