A meniscal cyst is a cystic mass that occurs in the meniscus area of the knee, mostly secondary to a meniscal injury to the knee. It may appear as a cystic mass in the knee joint area. As it is mostly associated with meniscal injury, it often presents with symptoms such as knee pain and interlocking. The cause of meniscal cysts: 1. Meniscal injury can cause contusions and blood accumulation in the meniscal tissue, or synovial cells are blocked in the meniscal laminae, and there is mucus secretion, which gradually increases and forms cysts. This is the main reason for the formation of meniscal cysts. With the further development of the lesion, the inner meniscus gradually forms a cystic protrusion to the outside, and finally forms meniscus laminae injury and meniscus cyst. Clinical manifestations: Chronic joint pain, pain after exertion or long walk, squatting pain, walking up and down stairs pain, which is reduced or even disappeared when resting, may be accompanied by night pain, some patients also have other manifestations. Some patients may have typical features of meniscal tears, such as joint interlocking, playing soft leg and popping. Physical examination: In some patients, an obvious mass can be seen in the joint space, which usually increases when the knee is extended and becomes smaller or even disappears when the knee is flexed. The swelling is hard and cystic in texture and may be associated with pressure pain; signs of meniscal injury may also be present. Ancillary tests: The main tests are ultrasound and MRI, both of which are non-invasive and have a high sensitivity and specificity for the diagnosis of meniscal cysts. Diagnosis: 1. History of trauma to the knee joint. 2, Knee pain with local swelling. 3, examination of the joint space can be found swelling, with pressure pain; often can appear meniscal injury signs. 4, MRI is the best means to diagnose meniscal cysts of the knee. 4, Confirmation of diagnosis relies on arthroscopy. Treatment: If it is clear that meniscal cysts are combined with meniscal injury, the best treatment option is arthroscopic surgery. Arthroscopy allows for exploration of the meniscus and, in addition to debridement of the cyst, also allows for management of the meniscal injury, including meniscectomy or suturing. If the cyst alone is removed without management of the meniscal injury, there may be residual symptoms and a high risk of recurrence of the cyst. If the cyst is too large, open surgery may be required to remove the cyst.