Diagnosis of meniscal injury generally requires the following aspects A. History Most often, the knee is suddenly rotated in the flexed position, and pain occurs immediately after the injury, accompanied by swelling of the knee joint. The pain and swelling can be relieved after rest. A small percentage of patients cannot recall the history of injury. When diagnosing, attention should be paid to understanding other factors such as the patient’s occupation and hobbies, whether the patient has worked in a squatting or semi-squatting position for a long time, and whether there is a history of joint instability or ligament injury. Some patients may not have obvious symptoms of knee pain and swelling, but mostly complain of popping and even locking of the knee joint when moving. Pain and impaired movement can occur when the knee is locked, and it is often necessary to shake or tug on the joint to release the lock. Symptoms Pain is the most typical clinical symptom, especially when going up and down stairs. The meniscus of the knee has no sensory nerve endings, and pain symptoms come from the irritation of the joint capsule at the torn part of the meniscus. Another typical symptom of meniscus injury is weakness of the knee joint. When the patient moves the knee joint, he/she suddenly feels weak, cannot control the joint movement, and even almost falls to his/her knees. The reason for this is that the quadriceps muscle force is weakened and cannot stabilize the knee joint; some scholars also believe that the contraction reflex and muscle strength of the quadriceps muscle cannot adapt to the requirements of stabilizing the knee joint after meniscal injury. A small number of patients have tears in the body of the meniscus, but there are no obvious clinical symptoms, and they are found incidentally during arthroscopic surgery for other problems. Third, the signs of meniscal injury 1, gap pressure pain: meniscal injury pressure pain point fixed, confined to a part of the knee joint gap. On palpation, with the flexion activity of the knee joint, the edge of the meniscus can be felt to protrude and indent. If the patient feels pain when the edge of the meniscus is protruding, i.e., “pain reproduction”, then it is very likely that the part of the meniscus is injured. 2, quadriceps atrophy: usually the earliest appearance of medial femoral muscle atrophy, long duration of the disease, thigh circumference thinning. 3, McSweeney’s sign (rotation squeeze test) positive: the examination method is to make the patient lie on his back, the examiner hold the heel with one hand, so that the knee joint to the maximum flexion position, then external rotation and abduction of the lower leg, the knee joint straight; the same method and then internal rotation of the lower leg and gradually straighten the knee joint. If pain or popping occurs, the test is positive. 4. Hyperextension and hyperflexion tests can help to determine damage to the anterior or posterior horn of the knee meniscus. Auxiliary diagnosis 1.X-ray: front and side x-ray of knee joint, patellar tangential radiographs have reference value for differential diagnosis, such as bone and cartilage injury, osteoarthritis, bone tuberculosis, bone tumor, patellar chondrosis, patellofemoral arthritis, etc. 2, ultrasound: ultrasound diagnosis is more popular in China, non-invasive examination, easy for patients to accept, and has some clinical application value for meniscal injury. However, because of the high rate of false negatives and false positives, the clinical application is relatively small. 3.Knee arthrography: Because it is an invasive test, knee arthrography should not be used as a routine test for the diagnosis of meniscal injury. 4, MRI examination: MRI is a reliable imaging technique for diagnosing meniscal injury of the knee, with the advantages of high accuracy, low false-positive and false-negative rates, and non-invasive, etc. The disadvantage of MIR is that it is more expensive. The MRI presentation of meniscal injury is graded as follows: Grade I: spherical or irregular signal within the meniscus without wave to the meniscal articular surface of the knee. Histology shows mucous-like degeneration of the meniscus of the knee. grade II: linear signal within the meniscus, which does not extend to the meniscal articular surface, but may extend to the meniscal capsule joint. Microscopy shows fragmentation and separation of fibrocartilage. Grade III: Intra-meniscal signal waves to the meniscal articular surface, suggesting meniscal tears. The meniscus barrel-handle tear is not easily visualized in the sagittal plane, and in the coronal plane it shows blunting of the free edge of the meniscus, with the torn portion entering the intercondylar fossa. Meniscal deformation (separation, fracture, and edge expansion), irregularity, or loss of most of the signal are also MRI manifestations of meniscal injury. The following manifestations suggest the presence of disc meniscus: (1) thickening of the body of the meniscus on the coronal plane compared with the healthy side (the difference between the edge and the center of the body of the meniscus is 2 mm); (2) increased height of the body of the meniscus on the sagittal plane in more than 3 scan sections at a thickness of 5 mm scan layer; (3) asymmetry of the meniscus on the cross-sectional plane and thickening of the body on one side. 5.Arthroscopy: The popularity of arthroscopic surgery, arthroscopic examination and microscopic repair and reconstruction in one phase, has solved many difficult cases of intra-articular injuries. The scope of application of arthroscopy has been broadened.