Most have a history of significant trauma. During the acute phase, the knee joint has obvious pain, swelling and effusion, and the joint flexion and extension activities are impaired. Some patients have the phenomenon of “interlocking”, or a popping sound when flexing and extending the knee joint. The site of pressure pain is usually the site of the lesion, which is important for the diagnosis of meniscal injury and for determining the site of injury. During the examination, the knee is placed in a semi-flexed position, and pressure is applied with the thumb along the upper edge of the tibial condyle (i.e., the edge of the meniscus) in the medial and lateral gaps of the knee joint, point by point from front to back. If the knee is passively flexed and extended or the calf is rotated internally and externally while pressing, the pain is more pronounced, and sometimes the meniscus can be touched with abnormal movement. 2. McMurray test (gyratory squeeze test) The patient lies on his back, the examiner holds the ankle of the calf with one hand and holds the knee with the other hand to flex the hip and knee as much as possible, then the calf is abducted, externally rotated and abducted, internally rotated, or internally retracted, internally rotated, or internally retracted, externally rotated, and gradually straightened. The presence of pain or ringing is positive, and the site of injury is determined according to the site of pain and ringing. 3. Powerful hyperextension or hyperextension test The knee joint will be strongly and passively hyperextended or hyperextended, such as the anterior meniscus injury, hyperextension can cause pain; such as the posterior meniscus injury, hyperextension can cause pain. 4. Lateral compression test The knee is straightened and the knee is forcefully and passively inward or outward. If there is a meniscus injury, pain is caused by compression at the affected joint space. 5. One-legged squat test Gradually squat from standing position with one leg holding weight, then stand up from squatting position, the healthy side is normal, when the affected side squats or stands up to a certain position, due to the squeezing of the injured meniscus, it can cause pain at the joint space, and even cannot squat or stand up. 6. Gravity test The patient takes the side lying position, lifts the lower limb for active knee flexion and extension activities, when the affected side of the joint gap down, because the injured meniscus is squeezed and causes pain; on the contrary, when the affected side of the joint gap up, there is no pain. 7. Grinding test The patient takes the prone position, the knee joint is flexed, the examiner holds the ankle with both hands and presses the calf downward while doing internal and external rotation activities, the injured meniscus causes pain due to extrusion and grinding; on the contrary, if the calf is lifted upward and then does internal and external rotation activities, there is no pain. X-rays: X-rays of the front and side can not show the meniscus damage, but can exclude other bone and joint disorders. Knee arthrography has little diagnostic significance and can increase patient pain, so it should not be used. MRI: The diagnostic accuracy is relatively high and can check the site and type of injury. Knee arthroscopy: Arthroscopy allows direct observation of the site and type of meniscal injury and other structures within the joint, and helps in the diagnosis of difficult cases. In conclusion, the diagnosis of meniscal injury is mainly based on the medical history and clinical examination. Most patients have a history of trauma, fixed pain and pressure energy in the affected joint space, and most of them can make a correct diagnosis by combining all the examinations and comprehensive analysis. For patients with severe trauma, attention should be paid to check whether there is a combination of collateral ligament and cruciate ligament injury. In advanced cases, attention should be paid to check whether there is secondary traumatic arthritis. The discoid meniscus is a thicker disk, vulnerable to injury, and is often bilateral. The main symptom is often a distinct crisp popping sound when the joint is moved. A mass can be felt at the lateral meniscus with pressure pain during joint movement. Mucinous changes after meniscal injury can produce meniscal cysts, with symptoms similar to those of meniscal injury, with a significant local mass, which is more pronounced when the knee is extended.