1, meniscal injury etiology and injury mechanism: Meniscal injury is usually due to sudden strong rotation in partial flexion of the knee joint under weight-bearing condition. When the meniscus is stretched or torn at the posterior periphery of the meniscus, the posterior aspect of the meniscus is squeezed toward the center of the joint and embedded between the femur and tibia. At this time, the joint suddenly straightens, causing a longitudinal tear of the meniscus. Most patients suffer from external violence or fall injury, but a few patients, especially those over 50 years old, may suffer from meniscal tears due to inadvertent movements in daily life, such as sudden squatting or sudden standing after squatting. 2.Diagnosis of meniscus injury: Even a senior orthopedic surgeon, it is not easy to make a definite diagnosis of meniscus injury through physical examination, which depends on the level of the clinician’s understanding of meniscus anatomy, biomechanics and pathology and the accumulation of clinical experience. Statistically, the misdiagnosis of meniscal tears can be controlled by careful history taking and experience, supplemented by standard imaging and arthroscopic techniques at a rate of <5%. < p=""> Symptoms: The typical symptom of a meniscal injury is pain located in the medial or lateral joint space, exacerbated by flexion and weight bearing, and often unbearable during squatting and kneeling. There is often a popping or bouncing sensation during knee extension and flexion activities, and most patients have symptoms of strangulation. Signs: Painful pressure in the joint space is the most common and main sign of meniscal injury. At the same time, there may be varying degrees of intra-articular exudate and quadriceps atrophy. Sometimes focal swelling can be found at the joint pressure points, especially when the knee is flexed. Special clinical tests include: (1) Apley’s test: the patient is placed in a prone position, the operator flexes the patient’s knee, applies pressure or pulls and rotates the patient’s lower leg to produce a grinding compression between the femoral condyle and the tibial plateau. (2) Steinman’s test: The patient is placed in the supine or sitting position, and the operator holds the patient’s ankle to flex the knee joint and rotate the lower leg at the same time. Both of the above methods are positive in terms of inducing pain in the joint space of the corresponding lesion. (3) Mcmurry’s test: The patient lies on his back, the knee is passively and strongly flexed. When examining the medial meniscus, the surgeon looks for the posterior inner corner of the joint space with one hand, holds the foot with the other hand, keeps the knee fully flexed, rotates the lower leg extremely externally, and then gradually extends the knee, and when the medial femoral condyle passes the torn meniscus, a popping sound can be heard or touched. When examining the lateral meniscus, the hand feels the posterior external angle of the knee and extends the knee after internal rotation of the lower leg. A negative Mcmurry’s test cannot exclude meniscal tears. 3.Imaging of meniscal injury X-ray can only exclude other lesions of bone or joint but has little diagnostic value for meniscal injury; X-ray can indirectly reflect meniscal injury, such as changes in joint space often suggest meniscal injury. In the past, arthrography was widely used to diagnose meniscal injuries with an accuracy rate of 60% to 97%, but its main drawback was its damaging nature. Nowadays, arthrography has been replaced by MRI, which is a non-invasive test with a high accuracy rate of 90-98%. 4.Treatment of meniscus injury The treatment of meniscus injury includes conservative treatment observation, arthroscopic meniscectomy and meniscus suture and meniscus transplantation. Stable tears less than 1 cm in length, which do not cause obvious mechanical symptoms, can be healed by conservative treatment and observation. Unstable tears that can cause mechanical symptoms should be treated surgically.