Knee replacement is possible at age 55. Generally speaking, for patients over 55 years of age who suffer from severe osteoarthritis, rheumatoid arthritis, traumatic arthritis, osteonecrosis or tumors, or severe pain or deformity of the knee joint, knee replacement is feasible when conservative treatment is ineffective. Knee replacement can also be considered for patients under 55 years of age whose symptoms seriously affect their daily life and for whom conservative treatment is not effective. Artificial knee replacement mainly depends on the patient’s condition, age is not an absolute determining factor for the operation, but because the knee prosthesis has a service life, in order to avoid the second operation, it is better to perform artificial knee replacement at an age older than 55 years old. Therefore, 55 years old can do knee replacement, but we should pay attention to the postoperative regular hospital review, avoid strenuous exercise of the knee in life.