The knee pain when squatting can be caused by the following reasons: First, meniscal damage to the knee joint. When there is a tear in the posterior horn of the meniscus, there can be pain on the back side of the knee when squatting, and this should be diagnosed and treated by early examination and MRI of the meniscus. Secondly, osteoarthritis of the knee joint. Severe osteoarthritis of the knee joint can involve the cartilage, meniscus and soft tissue of the knee joint, which can cause knee pain when squatting, and it is necessary to examine the X-ray and CT of the knee joint for diagnosis and treatment. Third, patellofemoral osteoarthritis of the knee, patellofemoral osteoarthritis patients can have pain caused by increased friction between the patella and femur when squatting, which should be diagnosed by X-ray and CT of the knee joint.