For the average initial total hip and total knee replacement surgery, the procedure is not complicated. Especially in total knee surgery, the entire process of osteotomy and prosthesis installation gives a mechanical, step-by-step appearance and is often perceived by beginners as not too difficult. Is this really the case? No, it is not. Here is a list of mistakes that surgeons are more likely to make. 1. The surgical operation is not very demanding and the technique is rough. For example, in total hip surgery, the implantation of the femoral stem prosthesis in the inversion position, the failure to reach the true bottom of the acetabulum in the process of grinding the acetabulum, resulting in an obvious gap between the acetabular cup and the acetabular floor, the tilting of the screws screwed into the fixed acetabular cup, resulting in the collision of the nail tail with the polyethylene lining, etc.; in total knee surgery, after the completion of the osteotomy, do not test whether the osteotomy block matches the preoperative measurement, do not test whether the lower limb force line is corrected, do not test the flexion gap for equivalence with the extension gap (which is the theoretical basis for total knee prosthesis design), etc. Although it is possible to make these mistakes and still get the surgery done, these problems can have a direct impact on the immediate and long-term results after surgery. 2. The theoretical basis is not solid, and intraoperative problems are difficult to cope with. Due to the influence of traditional concepts, surgeons in China are often equated with open-surgeons, as shown by the focus on operation, not paying attention to theory, not to mention well let the theory to guide practice. It is true that total hip and knee surgery is relatively simple when done smoothly, however, to deal with the problems that may be encountered during surgery cannot be based on experience alone, but also relies on a solid theory of joint replacement surgery to guide. For example, in total knee surgery, how to adjust the posterior tilt of the tibial prosthesis, how to determine the external rotation of the femoral condyles in the case of unclear anatomical markings, how to avoid posterior tilt implantation of the femoral condyle prosthesis, how to correct flexion contractures, how to achieve high flexion, how to avoid internal or external rotation of the tibial prosthesis (and if it occurs, whether it is better to be internally or externally rotated), and so on, are all examples of intraoperative tests of the surgeon’s basic skills. Without training in this area, a simple total knee surgery can be done in a messy manner. 3. There is no awareness of protection of the artificial joint material, resulting in scarring of the prosthesis. This is a common problem today. After the unsealing of the artificial joint prosthesis, the surface of the prosthesis (including the metal surface, polyethylene surface, ceramic surface, etc.) is often easily scratched by surgical instruments (vascular forceps, pull hooks, metal heads of suction devices, etc.) due to the doctor’s indifference to protection, and the damage to the surface of the prosthesis (even just a little) will significantly accelerate the wear and tear after use, which further leads to complications such as osteolysis in the long term. Of course, these problems do not affect the completion of the surgery and do not have serious consequences in the short term, so most surgeons are oblivious to them. But a qualified joint surgeon will try to avoid such rough handling, because he knows in his heart that there are four types of wear and tear of the prosthesis, and the surgical operation should reflect how to avoid these four types of wear as much as possible, so as not to damage the metal and polyethylene surfaces that make up the joint, and not to damage other parts that do not make up the joint surface. The unsealed prosthesis is brand new and must be intact when it is placed in the body! This is the basic quality of a surgeon operating in joint surgery. What types of wear are there?” Many surgeons are unable to answer such basic questions, and naturally do not pay attention to these small but important issues during surgery. Even if the surgery can be completed, it is inevitably a substandard surgery. In fact, there are many other problems such as these, so it is not convenient to go into them all here. The operation itself may not be too difficult for the joint surgeon, but it is not easy if the standards are high, depending on what the surgeon requires of himself. From this point of view, the patient seems to have to take his chances.