The knee is a weight-bearing joint, located in the middle of the lower extremity, and is susceptible to damage. The clinical manifestations of knee pain are more extensive. The common knee disorders are described separately: 1. Chronic arthritis is commonly seen in degenerative arthritis (osteoarthritis), rheumatoid arthritis, infectious arthritis, reactive arthritis, and gouty arthritis. The more common degenerative arthritis is described as follows: Degenerative arthritis is most commonly seen in the elderly, and its causes are mostly related to trauma, inflammation, age, malalignment of joint forces, or autoimmune reactions. The diseased joint can lead to destruction of the bone surface, subchondral bone necrosis, sclerosis and osteophytes, formation of bone spurs at the joint edge, narrowing of the joint space, unevenness of the joint surface and reduced joint fluid secretion, etc. Repeated injuries form an inflammatory response. As a result, knee pain, swelling, joint fluid accumulation, and unstable walking, joint deformity, extension and flexion are limited in advanced stages, and walking is difficult in severe cases. 2, chronic synovitis and quadriceps atrophy common knee synovitis are traumatic synovitis, inflammatory synovitis, tuberculous synovitis and syphilitic synovitis. Traumatic synovitis and quadriceps atrophy are described. Traumatic synovitis is caused by joint trauma, joint deformity, and uneven lines of gravity of the joint. This is accompanied by significant quadriceps atrophy, and the two often form a vicious circle, making treatment more difficult. Most of them are due to the degeneration of the quadriceps muscle strength with age after middle age, and the quadriceps muscle atrophy while the weight tends to increase. The quadriceps muscle atrophy prevents the joint from getting normal protection and is prone to trauma, which in turn stimulates the synovial membrane and inflammatory exudation, which in turn increases joint trauma, such as medial collateral ligament injury or knee cruciate ligament laxity. Therefore, the key to treatment is to establish muscle balance, reduce joint trauma, and eliminate inflammation. 3. Knee fat pad inflammation is often related to injury, and endogenous injury is more common, accounting for about 70%. All causes of fat pad gap reduction, such as synovial cysts and knee retroflexion, can cause symptoms and knee flexion pain. Exogenous injuries are mostly caused by trauma such as separation of the leading edge of the meniscus, fracture displacement, etc. 4, meniscal disorders are common: meniscal rupture, meniscal cyst and disc-like cartilage disc. The main symptoms are: knee pain, walking stiffness, difficulty walking up and down stairs, inflexible joint movement, frequent loss of step and fall, etc. 5. The common causes of popping knees are meniscal rupture, disc-like cartilage disc, and patellofemoral joint slippage. 6, bursitis around the knee joint common causes of bursitis trauma, septic infection is more common, and other diseases such as tuberculosis, syphilis, gout. 7. Osteochondral fracture of the patella is a frequently encountered but easily missed disorder, mainly due to trauma. It is mostly seen in athletes, dancers, military trainers and manual laborers, with young males being the majority of patients, mostly in the semi-curved position of the knee joint. 8, chondromalacia patella The cause is complex and is related to trauma, occupation, age and individual physique, especially when suffering from high patella, knee valgus deformity, etc. It is more likely to develop. The main symptoms are: discomfort and difficulty in expressing the affected knee, pain in the flexed knee joint, etc. 9. Osteochondrosis of the tibial tuberosity occurs mostly in young people and occurs at the tibial tuberosity epiphysis. The clinical manifestations are swelling and pain in the tibial tuberosity, localized significant elevation, and unbearable pain on the diseased side especially when the knee is flexed and kneeling, but walking is not affected and the pain is tolerable.