Thursday 2 January 2014

Knee arthroscopy for a torn meniscus

I have previously written that knee arthroscopy for osteoarthritis is no more effective than alternatives, including placebo. One criticism of those studies was that arthroscopy is usually done for a torn meniscus (often incorrectly called a torn cartilage) rather than arthritis, despite the facts that the original sham trial of arthroscopy included patients with meniscus tears, and later comparative studies looked specifically at patients with torn menisci. Now, however, we have evidence from a placebo-controlled trial of arthroscopic surgery performed specifically for a torn meniscus in patients without arthritis. Evidence that shows that while most patients improve after surgery, they improve equally well after placebo surgery.

The study was reported in the New England Journal of Medicine and included 146 patients with persistent knee symptoms consistent with a meniscus tear, a proven meniscus tear on MRI and no significant arthritis, who were randomised to either sham surgery or surgery to remove the torn parts of the meniscus (usual practice). Allocation was concealed, follow up was excellent, and blinding was extended to patients, researchers, assessors, and statisticians; even to the extent that the paper was written prior to unblinding.

The results showed that for all of the primary outcomes, there was no significant (or clinically important) difference between the groups (see image for a visual of the main outcome over 12 months). This was a high quality study, it is consistent with previous studies (here and here), and it showed very little difference between the groups for multiple outcomes over all time points, so the likelihood that there is any difference between real surgery and sham surgery is low.

Having established the validity of the study results, we now face the question of generalisability: do the results apply to you, or to other groups of patients? The study found no difference in the results if the patients had acute onset of symptoms or not, but excluded patients with traumatic onset. The results are therefore not generalisable to patients with acutely torn menisci or locked knees. The results are also not generalisable to patients with lateral meniscus tears, as it was restricted to tears of the medial meniscus. However, arthroscopies are most commonly done for patients with medial knee pain who have a torn meniscus on MRI, and/or a clinical picture consistent with a torn meniscus – exactly the type of patients that were included in this study.

“But patients seem to get better”
The other interesting thing about this study was that most patients got better anyway. This is very important because it harks back to one of my themes: people often improve after treatment, so the best way to reliably attribute that improvement to the treatment is to compare it against placebo treatment in a rigorous scientific test. If it fails, like arthroscopy has repeatedly, then the improvement seen was not directly due to the treatment.

“So what?”
The usual question that follows the explanation above is: who cares – if patients get better, why not keep doing the treatment? My answer to that has not changed much over time: 1) because of the financial cost (which I am not happy to bear); 2) because of the opportunity cost; 3) because it carries potential harm without specific benefit; and 4) because it removes the main separation between mainstream (science-based) medicine and alternative medicine (which survives on indirect and placebo effects).

The bottom line

If you have several months of knee pain that is consistent with a medial meniscus tear, and if you have a meniscus tear on MRI, your symptoms are likely to improve. Having the torn parts of the meniscus removed will not change that in any meaningful way.


  1. Thank you for the enlightening post, Dr. S. I had a knee injury from dancing, couple months ago and it spontaneously healed (pain subsided) but got reactivated when I resumed my dance classes. I got an MRI and it showed a medial meniscus tear. My doctor put me on diclofenax which (is pretty much the most horrible painkiller ever. worst three days for my GI) i discontinued soon after. He advised surgery.

    I got a second opinion from a different doctor who also advised surgery but asked me to do Contrast therapy for a week and also Rx trypsin/chymotrypsin for a week. I'm completely convinced by the study results (and the quality of studies) that surgery will not help me. My question is, would collagen injections/PRP injections have any effect on the rate of healing? To what extent does physiotherapy help in such cases?

    I realize I'm asking you advice on a specific case and I understand if you refuse to answer for legal reasons. Either ways, your blog and efforts are much appreciated! Thank you!



    1. Although this is snot an advice column, I can't help myself. I can tell you pretty clearly that collagen injections and PRP will not provide you with any significant benefit. Furthermore, NOT having the injections will benefit your bank account.

  2. Replies
    1. There are many things to do, including nothing (many people have difficulty with the concept of NOT treating conditions). It is easy for me to tell you what doesn't work, and sometimes, apart from simple analgesics and maintaining regular exercise, nothing else is effective. This means the patient might have to accept that the knee is no longer normal.
      I can't comment too much on specific cases without seeing the patient or the images, but many patients have difficulty accepting a knee that is less than normal as they age. This is what drives many people to have a joint replacement with only mild or moderate degenerative changes in the knee, because they get pain after volleyball or waterskiing. Those patients will not be happy with a knee replacement, as it provides a knee that is much worse than "normal".
      Other people cope well with the limitations that result from degenerative changes in the body.

  3. Very interesting, thanks. It may be my ageing demographic (mid 50s) but I have noticed an uptick in knee replacement surgery - is this the 'new' arthroscopy? Four friends have undergone knee replacement with very disparate recovery/success outcomes. Do you have a general view?

    Thanks again for an enlightening site.

    1. An "uptick" is an understatement. About 2/3 of joint replacements done these days are knees and the rate has been increasing for the last decade or two. I can't explain all of the reasons (ageing, obesity, demand, supply, lower thresholds, lack of alternatives) but I can tell you that the results are not as good as hip replacements. We are currently doing some research into the 'unhappy knee' and hope to have some insights into this problem in the next few years.

  4. It certainly seems plausible that removing a twisted piece of meniscus would prevent pain and locking.

    Having seen hundreds of menisectomies, it was always quite obvious when a mechanical blockage was removed and range of motion was immediately restored.

    I can see how a small tear may improve over time and even experienced it myself, however when your knee locks or gets sudden sharp pains from a piece of meniscus getting caught in the knee joint, surgery still makes sense to remove the flapping piece of cartildge. I've had three partial menisectomies under local, and was back to competing in a few weeks. Prior to one of my surgeries, I was hobbling on and off for 3 months while waiting for surgery. I was back to work within 3 days and competing within 3 weeks of my surgery. (Anecdotal, I know)

    It would be interesting to repeat the study and compare local anesthesia vs general anesthesia results as well. -Some general anesthesia agents such as ketamine, or alpha-2 agonists, may affect post operative pain.

    1. Yes, but having seen hundreds of meniscectomies, the true bucket handle tear and locked knee is uncommon, and I have seen many of these as chronic, with full range of knee movement. Most meniscectomies done are for very minor tears that are unlikely to be symptomatic.

  5. Dear Dr Skeptic, what is your opinion on meniscus scaffolds (Menaflex or Actifit) and meniscus transplants?

    1. I am not aware of any controlled trials of these devices. They would need to pass that test before I believed that they were helpful. There are too many similar things being used that have not been adequately tested, and either persist or are later shown to be ineffective.


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