The tendon pain behind the knee can be caused by several reasons: first, the popliteal fossa disease, when the popliteal fossa has bursitis or over the fossa cyst, can have the tendon pain behind the popliteal fossa, often swelling pain, in severe cases can be palpable cystic swelling and fluid manifestations. In severe cases, cystic swelling and fluid may be palpable. It is important to check the popliteal fossa with ultrasound and MRI for diagnosis and early treatment. Second, osteoarthritis of the knee joint, osteoarthritis of the knee joint can involve the soft tissues behind the knee joint and the meniscus and lead to tendon pain behind the knee, patients should check the X-ray and CT of the knee joint for diagnosis. Third, damage to the meniscus of the knee, when there is a tear in the posterior horn of the meniscus of the knee, there can also be tendon pain behind the knee, especially when the knee is bent and squatting pain is very obvious, to check the MRI of the meniscus to diagnose and treat.