The fuzzy logic of knee replacement surgery

Robin Wulffson MD's picture
knee replacement, orthopedic surgery, osteoarthritis, complications

Knee replacement surgeries are increasingly being performed in the U.S. and many other developed nations around the globe. Some of these surgeries are done for badly injured knees; however, the vast majority of procedures are done for advanced osteoarthritis. In the past, most of these surgeries were done on seniors beyond the age of 55; however, they are being performed more frequently on younger individuals. The upsurge in knee replacement with a variety of artificial joints has caused a number of medical experts to question who is an appropriate candidate for the procedure and whether the long-term outcome is beneficial. Patients are attracted to the operation in the hope that it will increase their mobility and reduce their pain; however, some patients will suffer complications—even death—from the procedure and others may not actually benefit from it in the long term.

Researchers based in the United Kingdom, Sweden, and Australia conducted a literature review going back to 1970 to evaluate the epidemiology (distribution and pattern of health events) of and risk factors for knee replacement to determine which patients should be candidates for the operation. They published their findings on March 6 online in The Lancet. Lead author Andrew Carr, FRCS FmedSci noted that the number of total knee replacements (TKRs) in the United States increased from 31.2 per 100,000 person-years in the period from 1971 to 1976 to 220.9 per 100,000 person-years in 2008, for a total that year of more than 650,000 procedures. The authors predicted that, in view of the increasing number of baby-boomers entering the senior ranks as well as the growing rate of obesity, the demand for TKRs will continue to increase in developed nations.

The authors wrote: "No clear consensus exists within the surgical community about exact indications, particularly severity of preoperative symptoms, obesity, and age." They referenced a task force organized by the Osteoarthritis Research Society International and a rheumatology organization that found that "pain, function, and radiographic severity are not associated with a surgeon's recommendation for knee replacement." Dr. Carr and his team noted that data regarding the safety and effectiveness of TKR surgery was “fuzzy.” They noted that most published reports of outcomes were single-surgeon or single-center case series. Furthermore, many of these reports are anecdotal accounts of procedures performed by the orthopedic surgeon who invented the implant. They wrote that in these instances bias and a potential conflict of interest tainted the studies.


The researchers focused on revision surgery—the need for a repeat operation—as the key outcome measure. The most common reason for revision surgery was “aseptic loosening,” caused by implant wear. This was more likely to occur in younger and more active patients. The second most common reason was infection. Other complications requiring revision surgery were postoperative pain, instability, and stiffness.

The researchers noted that the design of the implant could represent a major factor in minimizing or maximizing the risk for adverse events that require revision surgery. Therefore, they recommended that implants should be monitored through national registries. They also noted that the need for revision surgery could also be due to the preoperative diagnosis, surgical technique, surgeon’s experience and skill, patient factors, operating room conditions, and postoperative care. They also emphasized the need for “new strategies to treat early-stage osteoarthritis, which will ultimately reduce the demand for joint-replacement surgery.”

Take Home Message:
Many patients with knee problems are also overweight or obese. For these patients, a weight loss program could markedly reduce these symptoms. A variety of medications are available for the treatment of osteoarthritis. Before “going under the knife” it is prudent to consider the alternatives and obtain a second opinion. One should also ascertain the credentials of the surgeon, including medical school, specialty training, and board certification (i.e., the American Board of Orthopedic Surgery). The patient should also determine how many procedures the surgeon has performed. A general rule of thumb is at least 50.

Reference: The Lancet



Thanks Robin Wulffson MD, you share a very valuable info. Thanks for your article and website.
You are welcome. When an individual is suffering from chronic pain, they not infrequently opt for a quick fix via surgery. Unless the indications for surgery are clear, the surgery is expertly performed, and a postop complication does not occur, the outcome may fall far below a patient's expectations.
As an orthopaedic surgeon who specializes in TKR I spend a lot of time talking my patients out of knee replacement unless there pain and disability is severe and has failed non-operative treatment. It is rare however that patients actually lose weight - and keep it off. Unrealistic expectations of outcome are also common. I'd suggest to choose a surgeon who undertakes 50 / year and preferably > 150 / year and has undertaken a Fellowship in Joint Replacement. Overall , in the Australian Knee Registry, 10 year survival was 4-6 %, however this is a blunt measure of outcome.
Good points.