Pain in the bend of the knee when squatting can be caused by the following: 1, injury or tear of the posterior horn of the knee meniscus, which can have pain in the popliteal fossa when squatting, to check the MRI of the meniscus to diagnose; 2, popliteal cyst or bursitis of the popliteal fossa, these two diseases can have pain in the bend of the knee when squatting, which should be checked early, early examination of the ultrasound and MRI of the popliteal fossa to diagnose and Treatment. If the popliteal cyst is relatively large, surgery should be considered; 3, osteoarthritis of the knee joint, osteoarthritis of the knee joint often involves the meniscus of the knee joint and the soft tissue of the popliteal fossa, which can cause pain in the popliteal fossa of the knee after squatting, which should be examined by X-ray, CT and MRI of the knee joint for early diagnosis and treatment.