As the knee joint as the body’s heavy joints, its general morbidity to one side of the weight, the body’s self-protection will often choose to put too much weight on the side of the relatively good, but over time the other leg is also out of the problem, so the vast majority of patients visit the clinic is both sides of the pain, just one side of the heavy side of the lighter, then the question also comes, in the decision to accept the surgery of the patient asked the most is “Do I do both legs together or do I have separate surgeries?” Today I will give you an answer to this more common question. Generally speaking, the premise of whether to do both legs separately or together is that both sides have problems and cannot be solved by non-surgery. For some patients, one side of the knee is often very serious, but the other side is still in good condition (the surgeon grasps the indication for surgery based on the symptoms and signs and relevant examinations), and then there is no need to operate together, because the relatively lighter side may be due to the recent activity of the side to share the bad side of the body. The relatively lighter side may be in acute pain due to its recent activities to share the burden of the bad side, which will slowly be relieved after rest and treatment. In addition, the bad side will also return to its normal state after the surgery, which will relieve the burden of the non-operated side, and some patients avoid the surgery as a result. This assumes, of course, that the doctor you see is a reliable judge of your condition. If both knees need to be operated on, the question of whether to operate on one side and then the other, or both together, varies from person to person, but the advantages and disadvantages are as follows: Surgery time generally does not vary much between the two, and if the surgeon has already mastered the joint replacement very skillfully, the time for the operation on both sides together is generally no more than 3 hours, but if the operation is just being carried out, it is better to separate the operations. However, if the surgery is just started, it is better to perform the surgery separately, otherwise the long operation time will still have a great impact on the patient; in addition, the amount of perioperative bleeding and the possibility of blood transfusion are higher in bilateral surgery than in unilateral surgery; the perioperative medication and hospitalization time of bilateral surgery are smaller than those of separate surgery, and thus the cost is relatively lower; in addition, theoretically speaking, separate surgery is relatively lower for the perioperative risk of patients (the interval between the two operations is more than 3 hours). In addition, separate surgeries are theoretically less risky for patients in the perioperative period (>3 months between surgeries). Some patients think that separate surgery can be done on one side to recover for a period of time, at this time the functional exercise is not as difficult as after bilateral surgery, but this is also for different patients, if the deformity of the two legs are more serious, after the separate surgery breaks the patient’s previous walking habits, whether to let the knee after surgery to adapt to the original state, or to learn a new walking gait, at this time becomes a problem, often resulting in the postoperative functional training, and the patient will not have a chance to learn the new gait. Whether to adapt the postoperative knee to its original state or to learn a new walking gait becomes a problem, often resulting in poor postoperative functional training. There are two sides to every coin, and by the same token, there are advantages and disadvantages to having both sides operated on together and separately, which need to be carefully chosen after a comprehensive evaluation based on the patient’s own conditions, the surgeon’s judgment, surgical techniques, and perioperative management.