Total knee arthroplasty is an artificial joint replacement surgery that removes the joint surface that the body can no longer repair on its own and replaces the damaged joint with an artificial joint component to correct the force lines of the limb, eliminate knee pain, maintain joint stability, and restore knee function. Artificial knee arthroplasty was used later than hip arthroplasty, but it has a history of more than 20 years. Especially in recent years, knee arthroplasty has developed rapidly and solved some technical problems that used to be very difficult. Now, the safety and efficacy of artificial knee arthroplasty is as satisfactory as that of hip arthroplasty. Osteoarthritis of the knee (age-related osteoarthropathy) and rheumatoid arthritis are the most common forms of arthritis of the knee. In the advanced stages of arthritis, severe joint deformity and mobility impairment occur, and total knee surface replacement therapy is required at this time. Total knee surface replacement not only significantly reduces symptoms, but also corrects deformities and improves joint function, and has become one of the most common surgical procedures in developed countries in Europe and the United States. With the high bilateral prevalence of osteoarthritis, simultaneous artificial knee replacement on both sides has many advantages: 1. shortens the time of hospitalization and outpatient treatment; 2. reduces the cost of treatment; and 3. allows for a faster return to daily activities and a greater range of motion. Based on the above advantages, I advocate simultaneous bilateral replacement. In addition, for simultaneous replacement on both sides, we also compared with unilateral replacement, including the surgical results and the incidence of comorbidities, and there was no difference between the surgical results of staged replacement and simultaneous replacement at 2 years after surgery, and the incidence of comorbidities was not higher for simultaneous replacement than for staged replacement.