Study on placebo affect on knee surgery

Knee surgery placebo research study

This is a great scientific research study which found that people who only thought they had recieved arthroscopic surgery for osteoarthritis of the knee were recoving as well as people who actually did have the surgery.

The study highlights how the power of placebos and nocebos can be amazing and are often hugely underrated.

Trials like this are very rare, as it raises ethical questions about not treating a patient, even though such trials can demonstrate that the treatment (surgery or medicinal) is not necessary.

The placebo knee surgery approach

Dr Moseley randomly assigned 180 patients (165 completed the trial) with osteoarthritis of the knee to one of three groups:

Arthroscopic débridement, where full surgery was performed.
Arthroscopic lavage, where the joint in flushed with fluid.
Placebo surgery, where the patient was prepared in the same way, an incision was made in the skin and instruments were requested as normal. However, no surgery was performed inside the knee.

Neither the patient, nor staff providing precare and aftercare, were told which group had been assigned.

Patients were less than 76 years old, reporting on-going knee pain of at least 4 out of 10, having undergone medical treatment for at least 6 months. Severity of osteoarthritis of 9 or more, out of 12 had been excluded, as this relates to severe deformity of the joint.

What is the Placebo Effect?

The placebo effect is a beneficial effect on health, caused by positive expectations.

For example, when patients are given a sugar pill, rather than the real drug, but still get better.

Unfortunately, the result is rarely studied or published.

What is the Nocebo Effect?

Nocebo is a detrimental effect on health, caused by negative expectations.

For example, if a doctor in a white coat (increases subconscious suggestibility) says that "you could try this specific approach, but it doesn't normally work", then it is more likely that it will not work.

Or, if a doctor says that you have a cancer that only 5% survive. An expectation has been set.

Nocebo is the opposite of placebo.

Results of the placebo surgery

The results are quite amazing!

The débridement and lavage groups did not show any greater pain relief than the placebo group.

This was tested 1 year and 2 years after their operation.

The research team commented that:

This study provides strong evidence that arthroscopic lavage with or without débridement is not better than and appears to be equivalent to a placebo procedure in improving knee pain and self-reported function. Indeed, at some points during follow-up, objective function was significantly worse in the débridement group than in the placebo group.

You can read the full medical research study here.

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Placebo effect on knee surgery (Moseley 2002)

Knee surgery placebo research study

The placebo knee surgery approach

What is the Placebo Effect?

What is the Nocebo Effect?

Results of the placebo surgery