The arthroscope is inserted into the knee joint through a small 0.5M incision, and the lesion in the joint can be clearly and intuitively displayed on the monitoring screen, and then through 1~2 small incisions of 0.5~0.8M, instruments are inserted to remove, clean, repair and rebuild the lesion, making the examination and diagnosis and treatment completed in one time. The advantages include minimally invasive, safe, less bleeding, less postoperative reaction, and quick recovery of joint function. The following is a brief introduction of the diseases suitable for knee arthroscopy and treatment. I. Knee sports trauma: This is the area where the superiority of knee arthroscopy can be best demonstrated. With the improvement of people’s living standard and the increase of opportunities to participate in sports, such as basketball, soccer, skiing, military training, etc., knee sports injuries will gradually increase, and these injuries mainly include meniscal injuries and cruciate ligament injuries. In Europe, such as Germany, as long as there is blood in the joint after knee trauma, early arthroscopy is performed, which is conducive to early meniscal suturing, and the meniscal suture rate is over 80%, while the current meniscal suture rate in China is less than 20%, and the reason is that the meniscus has been damaged for many years, and the articular cartilage and meniscus are severely worn before they come to the clinic. In young patients with cruciate ligament injuries, especially anterior cruciate ligament injuries, if not treated early, the damage is significantly accelerated due to shear forces from joint instability that degenerate the articular cartilage. Therefore, when there is a blood joint after knee trauma, the joint has interlocking and instability, early arthroscopy should be performed, a phase of meniscal suture or molding should be performed to release the joint interlocking, and a phase or elective ligament reconstruction should be performed to restore the stability of the knee joint, which is beneficial to the recovery of knee function and prevention of osteoarthritis. Meniscal injury Anterior cruciate ligament injury Second, knee synovial crease wall syndrome: this disease is mostly seen in 35 years of age or older, more common in women, manifested as pain in the anterior medial aspect of the patella when the knee is flexed in 20-30° position, difficulty in going up and down stairs, pressure pain in the anterior medial aspect of the patella on examination, and the pain disappears after local sealing. The disease is seen arthroscopically as a stiff, thickened synovial tissue below the anterior patella, which is squeezed into the patellofemoral joint when the knee is flexed at 20-30°. The surgical result is good. Subsuperior patellar crease III. Knee joint free body: also known as joint rat, the free body can move in each interval of the joint and can cause joint interlock. The free body can be removed smoothly by arthroscopic observation of the intervertebral compartments of the knee joint. Free body IV. Osteoarthritis of the knee: As China gradually enters an aging society, osteoarthritis of the knee is one of the main reasons affecting the activities of the elderly. The occurrence of knee osteoarthritis generally increases significantly after the age of 55, and 35% of the elderly over 60 years of age in China have knee osteoarthritis, and weight is also an important cause of osteoarthritis. Other causes such as meniscus or ligament damage due to trauma, internal and external knee deformity, etc. Osteoarthritis of the knee can be classified as mild, moderate or severe. Severe patients can only be cured by artificial joint replacement, while most mild and moderate patients can have their pain relieved by non-pharmacologic and pharmacologic treatments, such as arthroscopic treatment for mild and moderate patients with poor results from conservative treatment, which can improve symptoms by 60%-80%. However, in some patients, symptoms reappear 1-2 years after surgery. Arthroscopic treatment of osteoarthritis is good or bad with the microscopic classification, the microscopic classification of OA can be divided into ① arthroscopic OA; ② synovial OA; ③ meniscal OA; ④ cartilage damage OA; ⑤ mixed type OA. which arthroscopic OA and meniscal OA the best surgical results, synovial OA is the second. If the articular cartilage is good, the force line is poor, and the surgical effect is good after performing osteotomy orthopedics, the onset time is less than 3 months, the effect is good. Severe osteoarthritis V. Contracture of the lateral support band of the knee: The patient may show pain in the upper and lower floors of the knee, pressure points at the outer edge of the patella, and the axial patellar slice (45° position) is obviously tilted outward. Arthroscopic release of the lateral support band can be performed. Sixth, septic arthritis of the knee joint, thorough flushing to remove pus moss under arthroscopic surveillance and placement of a tube for flushing is helpful to prevent joint stiffness. VII. Knee stiffness: If the knee joint has 20-30° mobility and no stiffness, complete intra-articular release can be performed under arthroscopy to avoid the large trauma of incision and release, which is not conducive to functional recovery. Diagnosis and treatment of other joint disorders: such as hip free body removal, ankle free body removal, treatment of ankle impingement syndrome, and diagnosis of shoulder joint trauma such as Bankart injury and Slap injury. Arthroscopic minimally invasive treatment of knee disorders is the main direction of joint surgery development, and it is believed that with further improvement of instruments and techniques, the level of treatment and results of joint disorders will be better.