Patients can usually determine whether the cast has loosened by the following methods. First, the plaster is not tightly adhered to the skin, and a large gap appears, and the patient often consciously feels that the plaster has moved, and even inserts his finger between the plaster and the skin; second, abnormal activities occur in the joints, especially common in the lower limbs of the long-legged casts, and the plaster is loosened after a period of time, manifesting itself as the knee joints or the ankle joints with abnormal activities, so that the joints which cannot be moved originally can be moved, which indicates that the plaster is loosened or has Third, the fracture has pain, when the cast is well fixed, the pain will be significantly reduced without movement of the fracture, when there is loosening, the fracture is again displaced, which can be manifested as obvious pain; Fourth, if the soft tissue swelling subsides after treatment for the fracture, then we need to pay great attention to whether the cast is loosened.