Knee fossa tendon pain hurts when you straighten it out, and it is considered to be related to trauma, lumbar disc herniation, popliteal cyst and other causes. It can be treated with general treatment, physical therapy, medication, surgery and other methods according to the cause. 1. Trauma: If there is any strain or contusion of the tendon after the knee fossa is traumatized, it will cause pain when the tendon is straightened out. After the injury, we should pay attention to rest, can be in the acute injury period of cold compress, in the recovery period of hot compress. Non-steroidal anti-inflammatory drugs such as diclofenac sodium can also be applied to relieve pain. If the injury is serious, plaster or brace can also be used to immobilize the treatment. 2. Lumbar disc herniation: when the herniated disc causes pressure on the nerve root, it will cause pain in the buttocks, back of the thighs, calves and feet, and also cause pain when the tendon is stretched. Usually pay attention to rest and develop good posture. Diclofenac sodium, methylcobalamin and other treatments can be applied. If the nerve compression is serious, there are surgical indications for surgical treatment, such as minimally invasive nucleus pulposus removal. 3. Popliteal cyst: it is a cystic mass in popliteal fossa, the cause of which is related to bursal disease, chronic injury, etc. It can also cause knee fossa tendon pain. When pain occurs, rest and avoid excessive activity. Diclofenac sodium can also be applied to relieve pain, and if the cyst is large and causes serious pressure on local tissues, it can be surgically removed. When the knee fossa tendon pain straightening pain, you can go to the hospital to further identify the cause of the disease, and then targeted treatment. The above drugs need to be applied under the guidance of a physician, avoid self-medication.