The knee joint is composed of the lower femur, upper tibia and skeleton, and is the most weight-bearing and high-volume joint in the body. The knee joint has the largest area of articular cartilage and the most synovial membrane, as well as the anterior and posterior cruciate ligaments and the medial and lateral menisci; functionally, the knee joint is not only a flexion and extension joint, but also has some ball and socket joint characteristics due to the shape and movement of the menisci. Therefore, the knee joint is not only able to flex and extend. It also has a certain range of rotational motion. These complex structures and multi-axis movements result in a high incidence of knee injuries and disorders, with meniscal tears accounting for more than 2/3 of cases, and injuries to the meniscus often result in joint pain, popping and locking. The meniscus has important functions such as absorbing shock, transmitting load, nourishing articular cartilage, lubricating and increasing joint contact area, and maintaining joint stability. Sports injuries and inflammatory diseases can cause meniscal damage. Severe damage to the meniscus will lead to early and progressive degeneration of the articular cartilage, eventually leading to osteoarthritis of the knee. The meniscus is a fibrous cartilage structure consisting of a complex three-dimensional meshwork of collagen, proteoglycans, and glycoproteins that transmits load, absorbs shock, stabilizes the joint, and transmits proprioception. Its main component is type I collagen, most of which is arranged in rings to resist tension; a small portion is arranged radially within the meniscus tissue to increase the tensile strength and stiffness of the meniscus. Only the peripheral part of the meniscus has a blood supply; the medial 2/3 of the meniscus usually lacks blood supply and is nourished by synovial fluid. The differences in the blood supply to the meniscus structure also lead to differences in the healing potential of the meniscus at different injury sites, and therefore different approaches are often used to repair the blood-supplied and ischemic areas of the meniscus. Treatment of meniscal injury Conservative treatment: In acute meniscal injury with intra-articular blood accumulation, muscle spasm affects the physical examination and makes clinical diagnosis difficult, so arthroscopic examination of the knee should be actively performed to determine whether there is concurrent injury to other tissues and structures to avoid misdiagnosis and omission. If there are no significant pathologic changes, conservative treatment is indicated to protect the torn tissue, reduce pain and swelling, and restore muscle tone and joint range of motion. The injury should be followed by braking, icing of the knee, and physical therapy for knee rehabilitation 3 days after the injury to gradually restore muscle strength and joint exercise and ambulation. At 6 weeks after injury, if there are no signs and symptoms, the patient can return to full ambulation; if there are signs of meniscal damage, arthroscopic knee surgery should be performed. Patients with extended, untreated acute meniscal injuries and patients with chronic injuries should also undergo arthroscopic knee surgery if signs and symptoms of meniscal tears are present on clinical examination. Surgical treatment: Knee arthroscopy not only provides a clear diagnosis of meniscal injury and corrects clinical diagnostic errors, but also clarifies the extent and degree of rupture, allowing for further determination of the specific surgical approach and scope, and allows for the management of other secondary or associated lesions in the knee joint. Knee arthroscopy can be performed as an emergency for early suspected meniscal injuries to shorten the treatment course, improve the treatment effect, and reduce the occurrence of injurious arthritis. The indications for surgery for meniscal injury are outlined as follows: (1) history of persistent pain and interlocking; (2) physical examination with limited joint compression, decreased joint mobility, and a positive special test for meniscal examination; and (3) exclusion of other causes of pain. The specific treatments for meniscal injuries can be divided into meniscal revision, partial meniscectomy, complete meniscectomy, meniscal repair, meniscal reconstruction, discoid meniscoplasty, allogeneic meniscus transplantation and meniscal tissue engineering reconstruction. Rehabilitation: The rehabilitation program is divided into 4 stages. Phase I: The goal of rehabilitation is to reduce swelling, relieve pain and promote tissue healing. This includes wearing a brace, moving the patella, ankle pump exercises, muscle training, and cold compresses. Phase II: The goal of rehabilitation is to protect the repair area and to train joint mobility. Brace settings: brace angle of extension/flexion 0°-30°, gradually increase flexion angle to >120° within the pain tolerance range; patellar mobility: normal range as possible; ankle pump exercises, knee compression exercises, skateboarding exercises, straight leg raising exercises; plyometric training: strengthening quadriceps, adductors, N cord muscles; weight bearing: first weight bearing on the toes (25% of body weight), gradually increase within the tolerance range. tolerance range was gradually increased. Phase III: Rehabilitation goal is to achieve full range of joint mobility; strengthening of plyometric training; brace angle of motion set at 0°-135° extension/flexion, weight bearing from 50% to 75% to 100%, de-bracing at 2 weeks; increased seated knee flexion/extension training to achieve full range of joint mobility without pain; progressive elastic band resistance training; power bike: 10-20 min per session, twice daily; micro-squat training; swimming training; and exercise. Squat training; swimming training; proprioceptive training. Phase IV: The goal of rehabilitation is to achieve motor function in muscle strength, joint mobility, and proprioception. Continuous elastic band resistance training; loaded straight leg raise; power bike training (increased resistance); swimming training; proprioceptive training; jogging training. The concept of tissue engineering offers hope for regeneration of meniscus tissue that is difficult to repair after injury. In patients with severe meniscectomy or postmeniscectomy, allogeneic meniscus transplantation can be performed to reconstruct meniscus function.