If a patient cannot bend the knee and has swelling, it is necessary to determine whether the patient has any special medical history: 1, such as a history of trauma, if there is a history of trauma, we should consider the internal form of the joint, structural damage, such as ligament damage, meniscal damage or fracture, joint edema caused by bleeding in the joint cavity; 2, if the patient does not have a history of trauma, we should ask the patient whether there is a history of metabolic diseases, rheumatic diseases or other medical history, according to If the patient has no history of trauma, we should ask the patient if he has any history of metabolic diseases, rheumatic diseases or other medical history, and determine the causes of joint swelling and inability to bend based on the medical history, such as redness, swelling, heat and pain in the joints and inflammation in the whole body, which may be caused by bacterial infections or special pathogenic infections that cause joint swelling and inability to bend; 3.