Osteoarthritis (OA) is a disease that produces pain and reduced mobility, and results in a decreased quality of life. It affects people of any nationality, race or gender, without preference for social or economic class, or level of education. When OA occurs in the knee, walking, climbing stairs, or sitting down and getting up become extremely painful. The condition may worsen over the years, and is often more severe in people who are overweight. Various medications, usually of the aspirin type (non-steroidal-anti-inflammatory drugs, or NSAIDs), physical therapy, complementary medicine (herbs, nutritional supplements), and body weight reduction are the main ways to try to manage OA.

If the wear-and-tear process in the joint leads to severe limitation of the knee movement, the sufferer may be unable to walk around without pain. In about 20% of those who have reached this level, disability is so bad that total knee replacement surgery (TKR) may be considered.

A recent survey of medical publications on TKR surgery has produced a number of answers to some important questions, which are summarized here:

Is total knee replacement an effective treatment for osteoarthritis?

Based on the results of the survey, the answer to this question should be "yes", even though studies making direct comparisons between non-operated and TKR-operated patients have not been done. TKR has been reported to be effective in reducing pain and disability in over 90% of cases due to OA. In a Swedish report of over 27,000 patients only 8% of them expressed themselves as dissatisfied with the result.

There's a big difference from country to country in the proportion of people with knee OA who actually have TKR surgery. Although OA is evenly distributed around the world, in some areas (such as the USA) between 200 and 1,000 inhabitants out of every 100,000 may have TKR, while in other countries (e.g. the United Kingdom) as few as 15 to 25 TKR surgeries per 100,000 inhabitants are done. This represents a 15- to 40-fold difference. Likely factors accounting for this are differences in health care delivery systems, varying expertise in OA treatment, and a lack of clear-cut standard criteria for major knee surgery. For instance, a UK survey shows that 2% of the population had pain and disability considered likely to make them candidates for TKR; this represents 2,000 per 100,000 inhabitants, while in fact only 15 to 25 per 100,000 actually receive TKR - or about 1 in 100 of possible candidates for this surgery.

Why, then, are people not given TKR more frequently?

The survey looked at reasons that might limit the use of this apparently successful procedure. These included differences in social class and ethnicity, as well as individual beliefs and expectations regarding the aging processes. Sometimes there is a general negative attitude towards surgical treatment for an arthritic condition, or even conviction that OA and pain are part of a normal, inevitable aging process. Complicating illnesses such as obesity, diabetes and heart disease can have variable effects on suitability for surgery. Obviously, the primary health care provider (usually the family physician) is an important player in helping determine whether TKR is an option. Referral of the patient to an orthopedic surgeon depends largely on an early diagnosis and assessment of severity of the condition, as well as existence of a good working relationship between the primary provider and a skilled surgical unit. The availability of qualified and experienced surgical teams can be a limiting factor, as well as economic considerations, especially if the patient has to pay.

Do orthopedic surgeons agree on the criteria for deciding to operate?

Although all agree that the severity of pain, limitation of movement, and radiographic appearance are the three major factors, there is no agreement on the exact degree of change that triggers the need for surgery; this is largely because standard ways of measuring these factors are not generally accepted. Perhaps more importantly, there is no good information on patients' own judgment as to which of them is most important.

It is certainly not easy measure pain and function in units that are meaningful to patients, but several test batteries have been used. One of these is the Western Ontario and McMaster Universities (WOMAC) Osteoarthritis Index, which is widely used to measure the degree of pain, stiffness and function in knee and hip OA. In time, tests such as these will make it easier for the patient to better understand what can be expected from surgery in terms of reduced pain, impaired function, and so on.

At present there are only a few official guidelines on TKR surgery available around the world. Orthopedic surgeons are aware of this, and of the need to further document the benefits and risks of the procedure, with more focus on the patient's role in evaluating the actual functional benefits and participation in the decision making process. Better education of both patients and their health care providers should improve in the situation, so that better-informed choices can be made. If the benefits and risks are better defined, sufferers will experience greater satisfaction regarding their choice to undergo this procedure.