Thousands of people could be undergoing unnecessary, risky and expensive surgeries as most procedures have never been subjected to the rigorous testing drugs are required to have, a leading surgeon has said.

Prof Andy Carr, an orthopaedic surgeon at Oxford University Hospitals, said there is emerging evidence that for certain types of elective surgery, the benefits could be partly or entirely explained by patients’ strong expectation that their symptoms would improve after treatment.

Previous trials, in which conventional procedures were compared with sham versions of the same surgery, found that there was no significant benefit beyond placebo for arthritic knee surgery, spinal cement injections for vertebral fractures, some gastric balloon procedures for obesity and certain forms of endometriosis surgery.

Carr said a wide range of other procedures ought to be investigated. “The correct thing has got to be to do the trials – not to continue doing operations where we don’t know whether or not there’s a strong placebo component or an entire placebo component because that means that tens or hundreds of thousands of patients are having unnecessary operations,” he said.

The issue is relevant for surgeries in which the improvements to health are subjective, for instance reducing pain or stiffness, which would account for a minority of all operations. “We’re not for one minute suggesting you should do placebo amputations or a placebo kidney transplant where there are very clear objective outcomes,” Carr said.

The comments followed a talk at Cheltenham Science Festival, called Is Pain All in the Brain?, by Prof Irene Tracey, Nuffield professor of anaesthetic sciences at the University of Oxford. Tracey has collaborated with Carr on the first placebo-controlled trial of the most common form of shoulder surgery.

She said there was a common fallacy that the placebo effect was all about “deception and fakery”. Her research shows that expectation can hijack the brain systems involved in pain perception and produce powerful physiological effects.

“We have to recognise that expectation is a completely normal part of our treatment,” Tracey said in an interview after her talk. “In the modern world where we’re trying to limit the amount of time physicians spend with patients we’re going in the opposite direction of what the science is telling us, which is that [expectation] is really important physiologically and therapeutically and we’re throwing that away.”

The shoulder surgery trial involves a procedure, called an acromioplasty, where a spur of bone in the shoulder is shaved off during keyhole surgery, the logic being that the spur causes pain when tendons rub against it. The operation is performed about 10,000 times each year in the UK, but until now its efficacy has not been tested in a randomised controlled setting. The study is currently under review with a journal.

Carr said that, while NHS commissioners are taking the issue seriously and are showing a keen interest in the outcome of the shoulder surgery trial, there has been greater resistance among surgeons, some of whom may view the suggestion that placebo plays a powerful role in surgery as an affront to their skill and expertise.

“There’s a huge amount of vested interest in all sorts of communities in terms of not accepting this is the case,” he said. “In many ways it’s much more confrontational than understanding that a tablet might be a placebo. Understanding that a procedure that you’ve been trained to do and that you’ve done all your life and that you’ve trained other people to do is simply a placebo: that’s pretty tough for surgeons to take.”

In future, he said, surgeons would need to become more open with patients about the possibility that placebo could play a role in the outcome and would need to look at other non-surgical ways to harness the placebo effect to achieve the same health improvements without placing patients at risk. “It seems difficult to me to justify an operation that has risk – albeit rare – if the treatment effect is just a placebo,” he said.

• This article was amended on 14 June 2017 because an earlier version said the results of the study are due to be published next month. The study is still under review with a journal and does not yet have a publication date.

