Every year, surgeons trim millions of damaged knee cartilages in a procedure so routine that most patients spend fewer than 24 hours in hospital. The logic seems airtight: if your meniscus is torn and your knee hurts, remove the torn bit. Pain fixed, function restored, patient goes home. It is, give or take, the kind of reasoning that feels self-evident. The kind you don’t really question.
A decade-long Finnish trial has just made questioning it rather urgent.
The results, published this week in the New England Journal of Medicine, are striking in their clarity. Patients who underwent partial meniscectomy (trimming of the degenerated meniscus) did not fare better than those who had sham surgery, in which surgeons made incisions and went through all the motions without actually cutting any cartilage. After ten years, the meniscectomy group had more symptoms. More reduced function. More osteoarthritis progression. And a higher likelihood of needing further surgery on the same knee.
The Finnish Degenerative Meniscal Lesion Study, known as FIDELITY, is one of the few surgical trials in history to use a placebo control, which is extraordinarily difficult to design and ethically fraught to run. Patients were randomised: some got the real operation, some got the sham. Of the original 146 participants recruited across five hospitals, more than 90 percent were still available a decade later for follow-up, a retention rate that would be enviable in a drug trial, let alone a surgical one.
Teppo Järvinen, professor at the University of Helsinki and the study’s principal investigator, puts it bluntly. “Our findings suggest that this may be an example of what is known as a medical reversal,” he says, “where broadly used therapy proves ineffective or even harmful.”
Medical reversals happen more often than medicine would like to admit. They occur when a treatment that seemed logical, that had been widely adopted and enthusiastically defended, turns out under proper scrutiny not to work at all. What makes partial meniscectomy a particularly vivid case is the gap between the evidence and the practice. Short-term trials had already raised doubts. Five-year data had already raised more. And yet, as Dr. Roope Kalske, a doctoral researcher who worked on the study, points out, “the procedure has remained widely used in many countries.”
The deeper problem is philosophical, really. Raine Sihvonen, co-principal investigator and specialist in orthopaedics, traces it to the surgery’s foundational assumption: that pain on the inside of the knee must be caused by a medial meniscus tear, which surgery can therefore fix. “Such reasoning, assumption based on biological credibility, is still very common in medicine,” he says, “but in this case, the assumption does not withstand critical examination.” Our current understanding points instead to age-related joint degeneration as the source of the pain; the meniscal tear visible on an MRI is often incidental, a marker of wear rather than the culprit. Cutting it out does nothing for the underlying condition and may, over a decade, make things considerably worse.
It’s a hard truth, and it carries a sting for patients who went through the procedure, and perhaps a sharper one for the surgeons who performed it. Partial meniscectomy is one of the most common orthopaedic operations globally. Hundreds of thousands are still performed annually in the United States and Europe (Finland itself has sharply curtailed the procedure in recent years, partly in response to earlier FIDELITY data). The surgery has a billing code, a recovery protocol, a cottage industry of physiotherapists trained around it. Entire careers have been built on performing it well.
Institutions Slow to Follow the Evidence
Which is, perhaps, why the institutions have been slow to move. Järvinen is candid about this. “For nearly a decade, many independent, non-orthopaedic organisations providing clinical guidelines have recommended that the procedure should be discontinued,” he says. “Still, the American Academy of Orthopaedic Surgeons and the British Association for Surgery of the Knee have continued to endorse the surgery. This effectively illustrates how difficult it is to give up inefficient therapies.”
There is something almost sociological about this pattern. The randomised evidence against partial meniscectomy has been building since at least 2013, when an earlier FIDELITY paper in the NEJM found no benefit at two years. Medium-term data held. Observational registry studies then began suggesting a possible link between meniscectomy and subsequent joint replacement surgery. The picture was consistent, it was growing, and it was being largely ignored by the professional bodies with the most direct influence over surgical practice.
Why Sham Surgery Matters
The sham surgery design deserves a moment’s attention, because it’s genuinely unusual and genuinely important. In drug trials, the placebo effect is routinely controlled for; every new medicine is tested against an inert pill. In surgery, this almost never happens. Patients know they had an operation; surgeons know what they did. The theatre itself exerts a powerful expectation effect, and that effect makes it very hard to know whether a given procedure is working or whether patients are simply responding to the ritual of intervention.
FIDELITY stripped that out. Patients in the sham group were anaesthetised, given arthroscopic incisions, their knees irrigated; everything happened except the cutting. That they subsequently reported outcomes comparable to, and in some respects better than, the real surgery group tells you something unsettling about how much of the perceived benefit of routine orthopaedic procedures might be expectation, not mechanics.
What Comes Next for Knee Pain
The findings don’t leave patients with a torn meniscus and a sore knee without options, though the alternatives are less dramatic than an operating table. Exercise therapy, load management, anti-inflammatories and, in severe cases, joint replacement (for actual end-stage arthritis rather than degenerative tears) remain on the table. The message isn’t that medicine can do nothing for the ageing knee; it’s that one particular mechanical fix, applied to a problem that may not be mechanical, probably wasn’t the right tool.
What FIDELITY leaves behind, beyond the data, is a question worth sitting with: how many other surgical procedures rest on similar chains of plausible-seeming logic that no one has properly tested? Surgery is difficult to trial, expensive to randomise, and professionally awkward to question. The sham surgery design is ethically complex and requires extraordinary patient commitment: more than ninety percent retention over a decade speaks to that. Running more such trials would take courage, money and a medical culture that’s currently rather better at performing operations than interrogating them.
Source: doi.org/10.1056/NEJMc2516079
Frequently Asked Questions
If my MRI shows a meniscal tear, does that mean I need surgery?
Not necessarily, and this research suggests you should be cautious about the default answer. Meniscal tears, particularly in middle-aged and older adults, are often a sign of normal joint aging rather than the direct cause of pain. The FIDELITY trial found that patients who had the cartilage trimmed did no better than those who had sham surgery, suggesting the tear visible on the scan may be incidental to what’s actually causing symptoms. Physiotherapy and exercise-based management are worth exploring with your doctor before considering an operation.
Is this the kind of surgery that’s still being recommended?
Yes, in many countries. Despite mounting randomised trial evidence stretching back more than a decade, major surgical bodies including the American Academy of Orthopaedic Surgeons have continued to endorse partial meniscectomy for degenerative tears. The FIDELITY researchers describe this as a textbook example of how difficult it is for professional bodies to abandon widely used procedures, even after the evidence turns against them.
Why does the sham surgery comparison matter so much here?
Without a placebo control, it’s almost impossible to know whether a surgical procedure actually works or whether patients improve because they expect to after going through an operation. FIDELITY used genuine sham surgery: anaesthesia, incisions, the full theatre experience, minus the actual tissue cutting. It found comparable or better outcomes in that group over ten years. That design is rare in surgical research and is exactly what makes this trial’s conclusions so difficult to dismiss.
Could partial meniscectomy ever be appropriate?
The FIDELITY trial focused specifically on degenerative meniscal tears in middle-aged patients, the most common scenario in which the surgery is performed. Acute traumatic tears in younger, active patients represent a different clinical picture, and the evidence there is less settled. The growing consensus is that it’s the degenerative, age-related tear where the surgery appears to offer no benefit and may carry real long-term risk.
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