The Surgery That Made the Knee Worse
Friday, May 8, 2026
Insteading · https://insteading.com/blog/microscopic-butterfly-wings/
A ten-year trial found one of the world's most common knee surgeries is not just useless. It accelerates the damage it was meant to repair.
What's happening
On May 6, the New England Journal of Medicine published the ten-year results of the FIDELITY trial. Finnish researchers had randomized 146 patients with degenerative meniscal tears to one of two treatments: real arthroscopic surgery, or sham surgery — where the surgeon mimicked the procedure without removing any tissue.
Arthroscopic partial meniscectomy is one of the most common orthopedic operations in the world. After ten years, with more than ninety percent of patients still in the study, the results are clear. The surgery group did no better on pain, function, or quality of life. And on the harder question — whether the surgery actually protected the knee — they did worse.
Twelve percent of the surgery patients eventually needed a full knee replacement, compared to four percent of the sham group. Arthritis progressed in eighty-one percent of the surgery group, against seventy percent of the controls.
What the Text says
The lead researcher, Teppo Järvinen, told reporters they had set out to prove the surgery worked. The reasoning made sense. Pain on the inside of the knee. A tear visible on imaging. A tool small enough to fit through a quarter-inch port. Of course it would help. Until the data came in and said it didn't.
The honest part of this story is that the people running the trial expected a different result.
Job 38:4"Where were you when I laid the foundations of the earth? Declare, if you have understanding.
The voice from the whirlwind isn't attacking Job for asking questions. It's listing — for four chapters — everything Job assumed he understood and didn't. Job had a model for why he was suffering. The model was coherent. It was also wrong. And the text takes its time letting the size of the world stand against it.
The reflection
The FIDELITY pattern is older than orthopedics. A community sees a problem, builds an explanation, acts on the explanation, and keeps acting on it long after the evidence has stopped supporting it. The major surgical societies still endorse this procedure. The researchers note how hard it is to give up a treatment once people have come to believe in it.
What's striking isn't that medicine got something wrong. It's that medicine, doing its slowest and most patient work, said so. The doctors who broke this story are from the same field that had been performing the surgery for decades.