Meniscal injury of the knee joint is a disease with limited pain in the knee joint, some patients have weak legs or interlocking knee joints, quadriceps atrophy, and limited pressure pain fixed in the knee joint space. Meniscal injuries are mostly caused by torsional external forces. When a leg is weight-bearing and the lower leg is fixed in semi-flexion and external booth, the body and the femur are violently rotated internally and the medial meniscus, between the femoral condyle and the tibia, is subjected to rotational pressure, resulting in meniscal tears. Symptoms Most have a history of significant trauma. During the acute phase, there is obvious pain, swelling and fluid accumulation in the knee joint, and the joint flexion and extension activities are impaired, after the acute phase, the swelling and fluid accumulation can subside on their own, but there is still pain in the joint when moving, especially when going up and down stairs, going up and down slopes, squatting and standing, running, jumping, etc. The pain is more obvious when moving, and in severe cases, there is limp or flexion and extension dysfunction, and some patients have “interlocking” phenomenon. 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 spaces 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 at the same time as the pressure is applied, the pain is more pronounced and sometimes an abnormally mobile meniscus can be palpated. 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 considered positive, and the site of injury is determined according to the site of pain and ringing. Strong hyperextension or hyperextension test The knee is strongly and passively hyperextended or hyperextended. If the anterior part of the meniscus is injured, hyperextension can cause pain; if the posterior part of the meniscus is injured, hyperextension can cause pain. Lateral compression test With the knee in the straight position, the knee is forcefully and passively inducted or abducted. If there is a meniscal injury, the pain is caused by compression at the affected joint space. One-legged squat test The patient is gradually squatted from the standing position with one leg holding the weight, and then stands up from the squatting position, the healthy side is normal, when the affected side squats or stands up to a certain position, the squeezing of the injured meniscus can cause pain at the joint space, and even cannot squat or stand up. Gravity test The patient takes the side lying position, lifts the lower limb for knee joint active flexion and extension activities, when the affected side joint gap down, because the injured meniscus is squeezed and causes pain; on the contrary, when the affected side joint gap up, there is no pain. The patient is in prone position with the knee joint 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 compression and grinding; conversely, 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 may increase patient pain, so it should not be used. 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 summary The diagnosis of meniscal injury is mainly based on 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. For advanced cases, we should pay attention to check whether there is secondary traumatic arthritis.