A fascinating landmark study of placebo surgery for knee osteoarthritis

PainSci » bibliography » Moseley et al 2002
updated Jul 3, 2026

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Twelve pages on PainSci cite Moseley 2002: 1. Extraordinary Health Claims 2. The Complete Guide to Low Back Pain 3. The Complete Guide to Patellofemoral Pain Syndrome 4. The Complete Guide to Plantar Fasciitis 5. The Complete Guide to Neck Pain & Cricks 6. Your Back Is Not Out of Alignment 7. Should You Get A Lube Job for Your Arthritic Knee? 8. Do Nerve Blocks Work for Neck Pain and Low Back Pain? 9. Knee Debridement is a Completely Ineffective Procedure 10. Does Cartilage Regeneration Work? 11. Classic examples of failed “common sense” in medicine 12. Knee surgery denounced by surgeons

PainSci commentary on Moseley 2002: ?This page is one of thousands in the PainScience.com bibliography. It is not a general article: it is focused on a single scientific paper, and it may provide only just enough context for the summary to make sense. Links to other papers and more general information are provided wherever possible.

This is landmark and fascinating study showed that people with osteoarthritis improved equally well regardless of whether they received a genuine surgical procedure or a sham.

From the abstract: “In this controlled trial involving patients with osteoarthritis of the knee, the outcomes after arthroscopic lavage or arthroscopic debridement were no better than those after a placebo procedure.”

Two decades later, this isn’t quite so surprising anymore — many similar studies have been done since — but it was a truly amazing result at that time. It is a particularly striking example of the placebo effect and implies that belief can have an effect even on seemingly “mechanical” problems.

In 2008, these specific results were fully supported by a Cochrane Collaboration review (Laupattarakasem) which concluded that “there is ‘gold’ level evidence that arthoscopic debridement has no benefit,” and by New England Journal of Medicine (Kirkley) which reported that “surgery for osteoarthritis of the knee provides no additional benefit to optimized physical and medical therapy.”

Surgeries have always been surprisingly based on tradition, authority, and educated guessing rather than good scientific trials; as they are tested properly, compared to a placebo (a sham surgery), many are failing. Moseley 2002 was the first of many to compare orthopedic (“carpentry”) surgeries to shams. By 2016, at least four more such procedures had been shown to have no benefit (Louw 2016), and that trend has continued since.

The need for placebo-controlled trials of surgeries (and the damning results) is explored in much greater detail — and very readably — in the excellent 2016 book, Surgery: The ultimate placebo, by Ian Harris.

~ Paul Ingraham

original abstract †Abstracts here may not perfectly match originals, for a variety of technical and practical reasons. Some abstacts are truncated for my purposes here, if they are particularly long-winded and unhelpful. I occasionally add clarifying notes. And I make some minor corrections.

BACKGROUND: Many patients report symptomatic relief after undergoing arthroscopy of the knee for osteoarthritis, but it is unclear how the procedure achieves this result. We conducted a randomized, placebo-controlled trial to evaluate the efficacy of arthroscopy for osteoarthritis of the knee.

METHODS: A total of 180 patients with osteoarthritis of the knee were randomly assigned to receive arthroscopic debridement, arthroscopic lavage, or placebo surgery. Patients in the placebo group received skin incisions and underwent a simulated debridement without insertion of the arthroscope. Patients and assessors of outcome were blinded to the treatment-group assignment. Outcomes were assessed at multiple points over a 24-month period with the use of five self-reported scores--three on scales for pain and two on scales for function--and one objective test of walking and stair climbing. A total of 165 patients completed the trial.

RESULTS: At no point did either of the intervention groups report less pain or better function than the placebo group. For example, mean (+/-SD) scores on the Knee-Specific Pain Scale (range, 0 to 100, with higher scores indicating more severe pain) were similar in the placebo, lavage, and debridement groups: 48.9+/-21.9, 54.8+/-19.8, and 51.7+/-22.4, respectively, at one year (P=0.14 for the comparison between placebo and lavage; P=0.51 for the comparison between placebo and debridement) and 51.6+/-23.7, 53.7+/-23.7, and 51.4+/-23.2, respectively, at two years (P=0.64 and P=0.96, respectively). Furthermore, the 95 percent confidence intervals for the differences between the placebo group and the intervention groups exclude any clinically meaningful difference.

CONCLUSIONS: In this controlled trial involving patients with osteoarthritis of the knee, the outcomes after arthroscopic lavage or arthroscopic debridement were no better than those after a placebo procedure.

original abstract †Abstracts here may not perfectly match originals, for a variety of technical and practical reasons. Some abstacts are truncated for my purposes here, if they are particularly long-winded and unhelpful. I occasionally add clarifying notes. And I make some minor corrections.

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