Pain behind the knee, i.e. popliteal fossa, may be associated with gastrocnemius bean syndrome, popliteal cyst, knee degeneration, and knee tuberculosis. When symptoms appear, it is recommended to go to the hospital for CT and blood tests to identify the cause, so that targeted treatment can be carried out to relieve the symptoms. 1, gastrocnemius bean syndrome: when overworked, traumatized, or strenuously exercised, inflammation of the tissues surrounding the gastrocnemius bean bone can occur, causing repeated pain in the lateral knee and popliteal fossa, and active hard nodules of bean size and obvious pressure pain appear in the popliteal fossa. After a clear diagnosis, clinical treatment with small acupuncture and closure is often used; 2. Popliteal cysts: can be caused by strenuous exercise and long-term strain. When popliteal cysts gradually increase in size, they may compress ligaments, blood vessels, nerves, etc., which can cause pain, usually accompanied by swelling after walking. If there are no obvious symptoms, it is necessary to avoid strenuous exercise and weight-bearing, which can usually be relieved by itself. If the pain is severe, surgery may be required to remove the cyst; 3. Knee degeneration: caused by aging or prolonged weight bearing, which can lead to meniscal damage, knee arthritis and other diseases, thus stimulating the popliteal fossa, resulting in significant soreness and pain. Cartilage-protective drugs such as glucosamine and chondroitin sulfate can be taken as prescribed by the doctor, while non-steroidal anti-inflammatory and analgesic drugs such as ibuprofen and diclofenac sodium need to be taken. In addition, attention should be paid to daily care of the knee joint, such as warmth and rehabilitation training to increase knee flexibility through abduction, adduction, forward flexion, and back extension; 4. Knee joint tuberculosis: mainly caused by the infiltration of Mycobacterium tuberculosis into the knee joint with blood, which can manifest as local pain, limited movement and other discomfort. In this case, anti-tuberculosis drugs, such as isoniazid and streptomycin, are usually used, and subtotal synovectomy of the knee may be performed.