For total hip and knee arthroplasty, thorough and careful preoperative preparation is particularly important. This includes the preparation of the patient’s general condition as well as the preparation of the surgical operation itself. In addition to a series of routine examinations upon admission, it is easy for the surgeon to overlook certain minor problems, especially hidden infections of the mouth, fungal infections of the feet (tinea pedis), urinary tract infections common in older women and lung infections due to prolonged bed rest. Being good at detecting hidden suspected foci of infection is a good quality necessary for a good joint surgeon, because infection is the number one enemy of artificial joint surgery, and postoperative intra-articular infection will directly lead to failure of the surgery and make subsequent treatment more and more difficult. In particular, we would like to emphasize the special infection “tuberculosis”, which sometimes causes hip and knee joint lesions and osteoarthritis, rheumatoid arthritis can be easily confused and requires a high degree of vigilance! Patients are advised to have routine preoperative laboratory tests for blood sedimentation, C-reactive protein, rheumatoid factor, anti-“O”, etc., and if necessary, PPD test and lung CT to exclude tuberculosis. In addition, it is important to follow up on the patient’s past infection history to provide a reference for selective precautionary antibiotics before surgery. Pre-operative arterial blood gas analysis is essential to enable the elderly patient to pass through the entire anesthetic process peacefully. In addition, the physician cannot overlook the assessment of pulmonary function. A complete set of pulmonary function tests is important for patients with a long history of smoking or pulmonary diseases such as senile lung disease. Lack of adequate preparation for the various contingencies that may occur during surgery is a common problem among joint replacement surgeons today. Due to the low threshold and quick start of artificial joint surgery, the attending surgeon often lacks awareness of the potential risks and is prone to take things lightly. (1) Pre-operative neglect of a comprehensive and careful special physical examination of the patient, lack of attention to the Harris score of the hip or the Knee Society score of the knee, and lack of collection and documentation of the patient’s pre-operative clinical data; (2) Failure to take full-length standing radiographs of both lower extremities before total knee surgery, or failure to take accurate measurements of the force lines of the lower extremities even if they are taken, resulting in intraoperative (2) Not taking full-length standing radiographs of both lower extremities before total knee surgery, or not taking accurate measurements of lower extremity force lines even if they are taken, resulting in intraoperative deviations in osteotomies that cannot be detected and corrected in time, and postoperative force lines that remain incorrect; ( 3) Not using templates to measure radiographs/CT films before total hip surgery. The oversized or undersized prosthesis that might be used during the operation was not prepared, and had to be temporarily delivered or replaced by other companies’ artificial joint products during the operation, resulting in longer operation time, more bleeding, and a much higher rate of intraoperative and postoperative complications! I have encountered many cases where the femoral head diameter was less than 40 mm, but the operation was successfully completed because of the pre-operative measurement and preparation of a special 38 mm bipolar head prosthesis or total hip prosthesis. I have also encountered very large femoral heads with a diameter of 59mm, and I have also encountered acetabulums with a grinding diameter of more than 62mm (because there is no non-cemented acetabular cup prosthesis larger than 62mm in China, a cemented acetabular cup was prepared as an alternative during the operation), so we must be prepared for various special sizes; ( 4) There was no adequate discussion and analysis before the operation, and the difficulties and ( 4) Insufficient discussion and analysis before surgery, and insufficient estimation of the possible difficulties and unexpected situations that may arise during surgery, so that it is difficult to cope with them when caught off guard intraoperatively, which ultimately affects the surgical outcome. For some cases that are difficult to operate, adequate preoperative preparation often takes hours or even days for analysis and discussion, which has far exceeded the short 2-4 hours experienced on the operating table. Sometimes the surgeon even needs to create a three-dimensional model of the prosthetic bone based on the results of CT 3D reconstruction and simulate the surgery on the model once in order to judge and solve possible tricky problems during the surgery in advance. As you can see, preoperative preparation is often decisive for the ultimate success of total hip and total knee replacement surgery. Be prepared, plan ahead, and sharpen your knife! Careful preoperative preparation guarantees the success of the patient’s surgery and reflects the good professionalism and dedication of the joint surgeon!