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Editorial: The New AAOS Guidelines on Knee Arthroscopy for Degenerative Meniscus Tears are a Step in the Wrong Direction

Leopold, Seth S. MD1

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Clinical Orthopaedics and Related Research: January 2022 - Volume 480 - Issue 1 - p 1-3
doi: 10.1097/CORR.0000000000002068
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Five years ago, I suggested in this space that the American Academy of Orthopaedic Surgeons (AAOS) revise its guidelines on arthroscopic surgery for degenerative meniscal tears [9], since the then-extant recommendations favoring surgery for this indication seemed to disregard the findings of numerous well-designed randomized trials that were available on the topic even then [5-7, 13, 15, 19].

The new version of the AAOS guidelines, which came out late last year [2], certainly is not what I had in mind when I made that suggestion. The new guidelines are a big step in the wrong direction.

The seemingly anodyne top-line recommendation (“Arthroscopic partial meniscectomy can be used for the treatment of meniscal tears in patients with concomitant mild to moderate osteoarthritis who have failed physical therapy or other nonsurgical treatments” [2]) conceals within it a multitude of sins. The biggest problems are that the new guidelines are at odds with the best-available evidence, they misuse the small amount of evidence they contain, and they are premised on the concept of offering surgery to patients who have “failed physical therapy or other nonsurgical treatments,” which itself is a failed concept as a basis to recommend surgery.

The new AAOS guidelines base their endorsement of arthroscopy for patients with moderate osteoarthritis and meniscal tears on three and only three studies that “compare outcomes following arthroscopic partial meniscectomy with physical therapy and demonstrate that knee arthroscopy with partial meniscectomy is as effective as physical therapy” [2]. In light of the numerous randomized controlled trials [4-7, 13, 15] and studies of other designs showing arthroscopy to be no better than nonsurgical treatments [1, 19], I’m flummoxed by how little evidence the guidelines call upon.

In addition to ignoring good evidence against the treatment they endorse, the guidelines misuse the evidence they point to. One of the three studies the AAOS references in the new guidelines is a 2-year report on a randomized controlled trial [4]; the authors of that study do not conclude in favor of arthroscopy, though the guidelines use those authors’ work as a basis to do so. The guidelines also missed the 5-year updated results on that trial [5]. That follow-up report specifically looked at the subset of patients who continued to seek care for pain after physical therapy and who subsequently chose to have arthroscopic surgery—the very group the AAOS guidelines focus on—and found those patients’ scores 2 and 5 years later were no better than patients initially treated with arthroscopy or those treated with exercise. In other words, intervening for patients with persistent symptoms did not move the needle for patients who had “failed physical therapy or other nonsurgical treatments” in any measurable way. And by citing only the earlier randomized controlled trial in the new guidelines instead of the more-recent report, the guidelines obscure an important part of the picture.

There were similarly serious problems with the way the AAOS guidelines used the other two studies they cited. In one [6], the AAOS used the fact that 30% of patients had crossed over from nonsurgical to arthroscopic treatment to justify surgery. This makes no sense. A patient’s decision to have discretionary surgery is largely driven by how surgeons present that option to them. Offering a patient an operation (or even a patient “asking” for one) is not evidence of that procedure’s efficacy, and the fact that surgeons recommend an intervention that has repeatedly been shown by high-quality evidence to be ineffective (indeed, no better than simulated or placebo surgery [15, 19]) obviously does not make recommending that intervention the right move. While surgeons may feel they know which patients should have this operation, our best evidence on surgeons’ abilities to peer into the future on this suggests that a coin toss would be just as good as a surgeon’s opinion [16], and the proportion of patients who do well with arthroscopy in this setting is not much better than what we’d expect from a surgical placebo [3, 8].

The only other study the new guidelines cited [17] determined that doing knee exercises was noninferior to surgery. As I mentioned, this unsurprising finding is consistent with the available evidence. What’s troubling is how the guideline writers flip it on its head and press it into service in support of the following claim: “The three studies … compare outcomes following arthroscopic partial meniscectomy with physical therapy and demonstrate that knee arthroscopy with partial meniscectomy is as effective as physical therapy.”

Torture the data long enough, I suppose, and they will confess to anything. But we should expect our operations to provide clinically important benefits and not merely that they be “noninferior” to nonsurgical treatments. As it turns out, this operation may in fact be worse than nothing. A 5-year follow-up study of a placebo-controlled surgical randomized controlled trial found arthroscopy for these indications indeed causes measurable harm: accelerated cartilage degeneration—the opposite of the desired effect—with no observed benefit in terms of patient-relevant outcomes scores [14]. That study, as well, was not cited in the recent AAOS guidelines.

We must deal with the fact that some patients’ knees will hurt. They’ll have meniscal degeneration and thinning cartilage—both are common findings in symptomatic as well as asymptomatic individuals. We also know the natural history of osteoarthritis, which tells us that some pain is likely to persist in many patients regardless of what we do with the meniscus or the articular cartilage, but with good coaching from an empathic surgeon, many of those patients can accommodate to their condition [11]. Given all that, what does it really mean for a patient to “fail” nonsurgical treatment [10]? We can’t expect physical therapy or cortisone shots to reverse arthritis or meniscal degeneration, and we shouldn’t call upon an unreliable operation when they don’t. Said another way, persistent pain in this context isn’t a failure: It’s an expected result.

In light of that, we should use our integrity and our empathy to engage honestly with patients about certain irrefutable facts—among them that our bodies change, and that physicians don’t always have the means to reverse those changes—and to inform this tough but essential conversation with the ample high-quality evidence on the subject that is available to us [1, 4-7, 13, 15, 19]. We have a duty to help patients get and stay healthy; it’s especially important to heed the call to that duty when solving the mechanical problem is not possible

Surgery, even arthroscopy, carries the potential physical harms associated with invading the body (infection, anesthesia, thromboembolism), as well pain and recovery time. It certainly has costs, which are not justified in the case of knee arthroscopy for degenerative meniscal tears [18]. In fact, the math in that study may be needlessly complicated; something that is not effective cannot, by definition, be cost-effective.

I will admit that I don’t know whether physical therapy really helps patients with these diagnoses, and in my heart, I don’t believe that it does. It doesn’t make a lot of biologic or anatomic sense to me. The same goes, of course, for arthroscopic surgery in this situation; these meniscal tears generally are not unstable and they usually don't subluxate into the joint (meaning they shouldn't cause the "mechanical symptoms" that we inappropriately blame on them), and the concept of smoothing articular cartilage that we know is going to continue to degenerate makes no sense to me, either. The “benefits” of surgery or physical therapy for degenerative meniscal tears are comparable in effect size to one another by all reasonable reports, and surgery’s benefits seem no different from those of a placebo [14, 15], even for patients with so-called “mechanical symptoms” [13]. What few benefits some observe from surgery or physical therapy may simply be attributable to the passage of time. I’m not sure.

What I do know is that recommending surgery to patients with meniscal tears and visible arthritis is at odds with nearly all of the best-available evidence. That makes it ethically problematic. We, and the AAOS, need to hold ourselves to a higher standard. Other standards—including a recent one from an international expert panel, which recommended with good reason against arthroscopy in nearly all patients with degenerative findings in the knee—are freely available for anyone who cares to look for them [12].

Five years ago, I hoped aloud that the AAOS would update its guidelines on arthroscopic surgery for degenerative meniscal tears [9]. I won’t make that mistake again.


The author would like to thank Joseph Bernstein MD, Terence J. Gioe MD, Paul A. Manner MD, and David Ring MD, PhD, whose comments helped to improve this essay.


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