The meniscus is located between the upper and lower articular surfaces of the knee and is divided into the medial meniscus and lateral meniscus, which are on the outside and inside of the knee joint respectively. The meniscus is often compared to a cushion because it absorbs shock during exercise, stabilizes the knee and protects the articular cartilage. However, the meniscus is also susceptible to tearing under excessive adverse stress. Most of the meniscus tissue has no blood supply, so it is difficult for it to heal on its own, but in the peripheral part of the meniscus, there are nutrient blood vessels distributed, so there is a possibility of healing for this part of the tear. Tears can cause the smooth surface of the meniscus to become uneven, which can cause pain, swelling and stiffness in the knee, and sometimes lead to “interlocking” of the knee. Although a person can still walk after a meniscus tear, it is still important to see a doctor as soon as possible to receive an early examination to determine the location and extent of the injury, otherwise it will cause more trouble for the knee in the future. The most common posture that causes meniscus injury is to use the affected foot as the fulcrum, and twist the knee in half-flexion, similar to kicking a soccer ball. Of course, repetitive squatting and standing, slipping and falling, bruising, and wear and tear from aging can all lead to meniscus tears. There are several common types of meniscus injuries. Radial tears, longitudinal tears, horizontal tears, or “barrel shank” tears, for example, can occur individually, or several types of tears can occur at the same time, creating a complex tear. There is also a congenital developmentally related type called a discoid cartilage tear, which often results in limited extension and interlocking of the joint. The location, type, and severity of the tear determine the surgical options. Generally speaking, meniscal tears due to sports injuries have a more defined history of injury. The patient will experience recurrent knee swelling, pain, and limited movement; sometimes there is a “weak leg” or painful popping. Over time, the thigh muscles may become atrophic and thin. During the consultation, the doctor will ask the patient about the history of the injury, the location of the pain, and the current condition that affects the activity. In order to prevent omission, the patient can also prepare a memo to remind himself before the consultation, so that he can express his problems in more detail. There are many conditions involving the knee, and for differential diagnosis, the doctor will have the patient lie down and examine the knee. One common test is called the “McKnight’s test”. The doctor will extend, flex and rotate the knee back and forth, which may cause pain and popping, but the patient does not need to be overly nervous, as the experienced doctor’s technique is measured. In addition, the patient may be asked to undergo X-rays, magnetic resonance imaging (MRI) and other tests to further clarify the diagnosis. Arthroscopic surgery has become the “gold standard” for meniscus tears. Typically, arthroscopic surgery requires only 2-3 small incisions of about 0.5 centimeters in the knee joint. This is a far cry from the old practice of cutting open the joint and removing the meniscus. The patient is hospitalized and first completes a series of routine tests to rule out any conditions that make him or her unsuitable for surgery. The surgeon makes a comprehensive evaluation and decides on a surgical plan. Anesthesia is administered after the patient enters the operating room. Generally, epidural anesthesia (half anesthesia) or general anesthesia is taken. In our country, epidural anesthesia is the most common, while in western countries, basically general anesthesia surgery. After anesthesia is reached the knee is in a flexed position. The surgeon will use an arthroscope to enter the joint cavity through a small incision to perform a thorough examination. All procedures are displayed in real time on a surgical monitor, sometimes with the patient watching. There are two ways to treat a torn meniscus. First, in cases of rupture of the free edge or severe compound injuries, the meniscus is partially removed, and in older patients with degeneration, the meniscus is also partially removed. The other is repair. When the tear occurs in the “red zone,” or “red-white zone,” the peripheral portion of the meniscus that is supplied with blood, a repair may be indicated at the discretion of the surgeon. The repair involves a detailed assessment of the nature of the injury, as well as a freshening of the injury site, and then access to special instruments to perform the repair. Since the repair instruments are extremely delicate and need to be performed in a very narrow gap, the surgery is quite difficult and the operator who is not skillful in the technique will rather lose out. There are a few more things that patients should know about meniscus surgery beforehand. Although meniscus surgery is minimally invasive, it does not mean that you will be able to move around a few days after the surgery. Rehabilitation is necessary; the removed portion of the meniscus cannot grow back, but the remaining meniscus can still function as a “cushion”; and the recovery from meniscus tear repair is slower than that of partial meniscus removal. According to our experience, the postoperative discomfort is slightly more pronounced than that of the resected meniscus. Although arthroscopic surgery is safer, complications, such as infection, hematoma, and vascular and neurological injuries, cannot be ruled out, but the chances of them occurring are very small. Of course, the meniscus may still tear again. After the surgery, the patient usually has to lie down more often, pay attention to elevate the affected limb, and apply ice 2-3 times a day to reduce swelling. Don’t forget about rehabilitation! At first, patients can do some extension and flexion of the ankle joint or tensing the leg in bed, and then transition to straight leg raise for quadriceps strength exercise. Flexion of the leg can be done in bed, but the range is controlled in the 60-90 degree range and can be gradually increased after 4-6 weeks. There is no problem getting off the floor, but at the beginning of the crutches, the affected leg can only be partially weight-bearing, walking with a straight leg or slightly bent, and gradually full weight-bearing and increased bending after 4-6 weeks. However, patients with meniscus repair should not do deep squatting for 12 weeks. Finally, don’t forget to follow up regularly, the guidance and advice of the attending surgeon is of utmost importance to your postoperative recovery.