Osteoarthritis of the knee, a debilitating and painful disorder characterized by the loss of essential joint cartilage, strikes 12 percent of the U.S. population aged 65 years and older. To alleviate the symptoms of this disease, doctors typically recommend medication and physical therapy. But these treatments often fall short of full pain reduction, leading many patients to undergo expensive arthroscopic surgery. Most individuals report an increase in movement and a lessening of pain following the procedure, but no one knows exactly why these effects occur. Additionally, no large-scale study has yet examined how much of the patients improvement can be attributed to placebo effect alone. To that end, new work published in the current issue of the New England Journal of Medicine should prove insightful. Surprisingly, sham surgery seems to alleviate painful symptoms just as effectively as the real operation does.

Arthroscopic surgery in the knee--an operation that uses a pencil-thin instrument to peer inside the damaged joint--comes in two forms: debridement, in which loose or worn cartilage is cut away, and lavage, in which the bad cartilage is flushed out with liquid. In this study, J. Bruce Moseley of the Houston Veterans Affairs Medical Center and his colleagues randomly placed 180 osteoarthritis patients into three treatment groups: debridement, lavage, or sham surgery, in which a surgeon would make incisions in the knee, but not cut or wash out any cartilage. Neither the patients nor their health care providers knew which group the researchers had placed them in. For two years, patients continually evaluated their knee pain, while doctors examined their walking and stair-climbing abilities. The results show that at every point in the investigation, all three groups reported an equal degree of reduction in pain and increase in activity level. Moseley and his collaborators thus conclude that the placebo effect can account for the observed improvements; the surgeries do not appear to have any significant effect on the actual physiology of the disease.

In response, critics say that surgeons sometimes operate only on the people they feel will benefit most from the surgery, as opposed to treating them randomly, as this study did. Other researchers argue that it just makes sense to get rid of floating debris in the joint that may get in the wrong place and trigger pain. But in an accompanying editorial, David Felson of Boston University and Joseph Buckwalter of the University of Iowa note that "Although smoothing cartilage and [other] irregularities may sound appealing, larger forces within and outside the joint environment, such as malalignment, muscle weakness, instability, and obesity may have greater effects on the clinical outcomes of osteoarthritis of the knee."

The new findings could transform the treatment of osteoarthritis. "This study has important policy implications," remarks lead investigator Nelda Wray of the Houston VA Medical Center and Baylor College of Medicine. "We have shown that the entire driving force behind this billion dollar industry is the placebo effect. The health care industry should rethink how to test whether surgical procedures, done purely for the relief of subjective symptoms, are more efficacious than a placebo." --Rachael Moeller