Total Knee Replacement Part I

Abstract

Total knee replacement has been one of the most common elective surgical operations in the United States for the past 20 years. The most common indication for total knee replacement is primary osteoarthritis with severe knee pain or limitation of function. Other indications include rheumatoid arthritis, posttraumatic osteoarthritis, and tumor reconstruction. Unlike total hip replacements, total knee replacement has no role in the primary treatment of fractures or dislocations of the knee. Approximately 10% of the U.S. population over age 55 years has osteoarthritis of the knee with disabling symptoms.1 As the baby boomer generation ages and moves into the prime years for joint replacement (age 50 years or older), the prevalence of total knee replacements can be expected to increase. In one study of the use of total knee replacement in western Europe, among the population over age 65 years the annual rate of total knee replacement was 0.5% to 0.7%.2 If the rate is similar in the United States, approximately 200,000 knee replacements would be performed per year in this country in patients over 65 years of age. The number of total knee replacements performed in the United States per year actually is approximately 350,000. Cost-benefit analyses have indicated that knee replacement not only is effective in eliminating pain and restoring function,3 but also is actually cost-effective compared with the alternative of pharmacologic pain control.4 Knee replacement surgery also is cost-effective at a societal level compared with common treatments such as coronary artery bypass surgery and renal dialysis.5 The knee joint replacement industry generates approximately $10 billion in revenue per year in the United States, taking into consideration only the prostheses and related instrumentation, not the patient evaluation, surgery, hospitalization, rehabilitation, or other medical costs. The total cost of a total knee replacement operation, including the prosthesis and the medical bills, is similar to that of an automobile. Direct-to-consumer marketing on the part of manufacturers of knee replacement hardware can be expected to further increase the demand for these operations in the United States. The science of joint replacement surgery currently is one of the most active areas of research in orthopaedics. Radiologists must understand when diagnostic imaging of knee replacements is appropriate, and how to perform and interpret these studies. In this first part of a two-part series on total knee replacement, we review the different types of total knee replacements and their normal appearance on imaging. In the next issue, we will review the imaging features of common complications.