The human body is like a sophisticated machine, and joints can be replaced with new ones when they are “obsolete” due to injury or disease. The world’s material industry is now well developed and the manufacturing process is sophisticated, and various artificial joints can successfully mimic human joints. The joints that can be replaced are the hip, knee, ankle, shoulder, elbow, wrist, etc. Even the finger joints can be replaced. The earliest and most frequently replaced joints are the hip joints, with more than 2 million hip replacements worldwide each year. Knee replacements are technically more difficult than hip replacements, but as medicine continues to advance, knee replacement methods are becoming more and more sophisticated and effective. Joint replacement is not “removing the original joint and replacing it with a stainless steel one”. The surgery is like peeling an apple to remove the surface of the broken cartilage and install a surface replacement prosthesis to restore mobility, relieve pain, and correct deformities. How many patients need joint replacement Osteoarthritis caused by degeneration of the bone joints in the elderly is the most prevalent and influential joint lesion in the systemic osteoarthritis. In some advanced developed countries, such as the United States, more than 500,000 patients need a joint replacement each year, with the number of knee joints greatly exceeding the number of hip joints. Which knee joints can be replaced Knee replacement, is one of the most effective procedures for treating advanced or severely degenerated knee osteoarthritis. After long-term observation, the long-term results are also satisfactory. Foreign countries have reported 1000 cases of knee arthrosis with a 97.3% success rate of surgery. In addition to degeneration-induced osteoarthritis, rheumatoid arthritis, infectious arthritis, trauma-induced joint deformity, joint pain and obvious destruction can be considered for replacement. For patients with bone tumors of the distal femur or proximal tibia that can preserve the limb, the tumor segment can be removed and replaced with a specially designed artificial knee joint. With joint replacement, patients can improve their quality of life and even get a chance to work again. Some people think that replacing the old knee with a new one involves removing a lot of bone and causing too much damage. This is not the case. The surgery only removes the surface of the broken cartilage like peeling an apple, the rest of the joint does not move. Patients can be on the floor 3-5 days after surgery and practice walking with the help of crutches or a walker. After rigorous rehabilitation exercises under the guidance of the doctor, the replaced knee joint will be able to move freely.