This is the most common cause. Patients with osteoarthritis of the knee often have narrowing of the medial and lateral compartments of the knee and damage to the cartilage, which leads to increased pressure on the medial and lateral compartments after prolonged standing, resulting in pain in the knee, which should be diagnosed and treated early by examining x-rays and CT of the knee. Second, the knee meniscus injury, when the knee meniscus has a tear, can also have after standing for a long time knee pain symptoms, this is due to long standing after the meniscus by the femur, tibia compression, and cause pain, this time to check the meniscus MRI to diagnose. Third, hip joint disease, when the hip joint has femoral head necrosis or impingement syndrome, after standing for a long time can also have knee pain, which is a kind of radiological pain, then we should check the hip joint x-ray, MRI to diagnose.