Sedentary standing up knee pain can be caused by physiological reasons, osteoarthritis and meniscus damage. 1. Physiological reasons: may be because of the long sitting, the back side of the leg nerves and blood vessels for a long time by the extrusion, resulting in insufficient blood supply to the legs, thus appearing sedentary stand up knee pain can not straighten the situation, usually rest for a period of time will be significantly improved. 2. Osteoarthritis: this kind of disease may be due to chronic joint strain, trauma and obesity and other factors, often manifested in sedentary joint pain, usually accompanied by swelling, deformity symptoms, will also appear to stretch the situation. 3. Meniscus injury: If the patient has a history of knee sprain or strain, meniscus injury may occur, and the degree of injury is more serious, and even swelling and impaired mobility, which leads to sedentary standing up knee pain after the fossa can not straighten the phenomenon. If the symptom of pain in the back of the knee after standing up for a long time cannot be relieved, it is recommended that the patient go to the hospital for a detailed examination in time to identify the cause of the disease and then targeted treatment.