1, osteoarthritis of the knee joint mainly manifests as joint swelling, pain, stiffness, deformity and functional impairment. Intermittent pain in the early stage, pain at night is obvious in the middle and late stage, and inversion deformity of the joint is visible. Clinically, osteoarthritis of the knee can be diagnosed if the following 1, 2, 3, 4 or 1, 2, 3, 5 are met: ① Recurrent knee pain within the last month. (ii) Frictional sound during activity. ③Morning stiffness of the knee joint ≤ 30 minutes. ④Middle-aged and elderly patients (≥40 years old). ⑤ hypertrophy of the bony end of the knee joint with osteophytes. 2, meniscal injury Patients often have a history of knee sprain, accompanied by knee swelling, pain and dysfunction, and often have “interlocking symptoms” during joint flexion and extension activities. Swelling, pain and atrophy of the quadriceps muscle are common. 3. Knee synovitis (1) Acute synovitis The joint swells rapidly after injury and gradually worsens, with protective spasm of the muscles around the knee joint, limited extension and flexion, positive floating patella test, increased local temperature of the joint, and generalized hypothermia. (2) Chronic synovitis The knee joint is swollen, sore, limited in movement, and has a positive floating patella test. The thickened synovial membrane has frictional sound and pressure pain when touched, and there may be joint ligament laxity and articular cartilage softening in long-standing disease. 4, intra-articular free body Patients can often feel the intra-articular free body, sudden onset of severe pain in the knee joint when moving, and sometimes the patient can fall. The knee joint may suddenly lock up and cannot be extended or flexed. The joint swells and fluid accumulates, which can lead to chronic synovitis over time. 5, chondromalacia patella This disease is mostly seen in women and starts slowly. Patients mostly have a history of overexertion of the knee joint with half squatting, or a history of knee impingement. Early manifestation is knee tenderness, weakness in going up and down stairs, and later intermittent pain on the deep surface of the patella, aggravated when sitting or kneeling or squatting with the knee bent, knee tenderness and instability, especially obvious when going up and down stairs and when the joint starts to move, and finally pain even when walking and jumping. In long-standing cases, quadriceps muscle atrophy and joint effusion are seen. Pressure pain around the patella and patella. 6, anterior cruciate ligament injury of the knee anterior cruciate ligament rupture is mostly the result of forceful knee hyperextension or forceful abduction injury. Patients feel a tearing sound in the knee joint at the time of trauma, followed by weakness, severe joint pain, rapid swelling, blood accumulation in the joint, and petechiae around the joint suggesting joint capsule injury and joint dysfunction. Patients with old injury may experience quadriceps atrophy, a sense of playing with a weak leg or misalignment, and a decrease in motor ability. 7, posterior cruciate ligament injury of the knee Injury of the affected knee can be heard tearing sound or tearing sensation to the ground, severe pain in the knee, rapid swelling, blood accumulation in the joint, petechiae around the joint suggests joint capsule injury, joint instability and dysfunction. 8, medial and lateral collateral ligament injury of the knee joint After the injury, the medial or lateral knee joint pressure pain is obvious, the inversion or valgus test is positive, the activity is painful, and the joint is unstable in severe cases.