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The orthopedic community faces a number of myths regarding the causes of knee pain. A large number of physicians believe that cartilage loss in the knee causes pain and/or that a meniscus tear also causes pain. The problem is that recent medical research isn’t cooperating.

myth 1: cartilage loss causes pain

Cartilage is a cushion for a joint that covers both ends of the bone. When you lose cartilage from a joint like the knee, this is one definition of arthritis. Almost every physician believes that cartilage loss is the cause of knee pain, and most patients are focused on cartilage. Is it good? Is it bad? How much is there? What if the big-time research of the last five years actually showed that this concept was a myth?

Two very large, ongoing studies are tracking patients with osteoarthritis of the knee, using many different modalities such as X-ray, MRI, exams, blood work, questionnaires, and biomarkers. Both sponsored by the National Institutes of Health, the Osteoarthritis Initiative and the Framingham Osteoarthritis Study have felled many orthopedic myths to date, not the least of which is the idea that cartilage loss equals pain.

Analysis of data from the Framingham study shows that among more than 700 patients who had no evidence of osteoarthritis on X-ray, many middle-aged and older patients had MRI findings of osteoarthritis. Here’s what the authors reported in this group:

“The prevalence of (bone) attrition (38% v 30%; P=0.04), bone marrow lesions (59% v 50%; P=0.03), and subchondral cysts (31% v 23%; P=0.04) was higher in participants with painful knees than those without pain (table 2). The prevalence for the other features were within about 4% of one another among painful and painless knees with no significant differences (table 2). Indeed, the prevalence of at least one type of MRI detected pathology (“any abnormality”) was high in both painful (91%) and painless(88%) knees(table 2⇓). Regardless of the definition of pain used, MRI detected abnormalities were highly prevalent in people with (90-97%) and without (86-88%) knee pain. While the prevalence of MRI abnormalities was not significantly different in those with versus those without knee pain for most definitions of pain we tested, the prevalence of “any MRI abnormality” was higher in those with WOMAC pain compared with those without pain (P=0.002). Even so, the prevalence of any MRI abnormality was as high as 86% in those without WOMAC pain.”

What the Framingham data boils down to is that problems in the bone were the only thing associated with pain. All of the rest of the problems seen on MRI that almost all doctors would think should be associated with knee pain, weren’t.

The other major study, the Osteoarthritis Initiative, looked at cartilage loss in almost 500 patients. Analysis of that data also showed that the amount of lost knee cartilage on X-ray and MRI wasn’t strongly associated with pain.

The conclusion of this last study: Osteoarthritis is a multifactorial processs, and the need is to treat patients based off their symptoms and rely on radiographs as confirmatory modalities and not as diagnostic modalities. Translation? If your doctor is looking at an X-ray or MRI and concluding that he knows the cause of your pain without a thorough exam, find a new doctor.

myth 2: meniscus tears in middle-aged or older patients cause pain

The meniscus is a spacer for the knee that cushions the cartilage surfaces. It makes some sense that tears in this structure would be considered a big deal. Research published in the September 2013 issue of Radiology journal suggests that a certain type of meniscus tear may be associated with more rapid onset of osteoarthritis. At present, however, we have no idea whether a special type of meniscus tear causes the osteoarthritis or is just a feature of it.

Not a second goes by during the work week in the United States without some middle-aged patient showing up in a doctor’s office with MRI in hand and the conclusion is that the meniscus tear seen on the images has begun causing knee pain. The very common solution doctors take is to perform surgery to remove that meniscus tear. Based on the high-level medical research performed to date, this is the one of the biggest medical boondoggles of the last century.

The first issue is whether there is any data that a meniscus tear seen on the knee MRI of a middle-aged or older person causes knee pain. Research published September 11, 2008, in The New England Journal of Medicine showed that knee meniscus tears in such patients don’t cause pain—that is, knees with meniscus tears are very common in middle-aged or older patients with and without knee pain. In fact, in the February 2014 issue of the British Journal of Sports Medicine an academic researcher commented that meniscus tears in this patient population are as common as wrinkles and should be treated accordingly.

The following three high-level studies suggest that knee arthroscopic surgery is of no help to middle-aged and older patients:

  • In its September 2008 issue, The New England Journal of Medicine reported that arthroscopic knee surgery to “clean up” a painful knee is no better than fake surgery for patients with osteoarthritis of the knee.
  • In its May 2013 issue, The New England Journal of Medicine reported that arthroscopic knee surgery doesn’t help middle-aged knee-pain patients with meniscus tears and mild to moderate osteoarthritis any better than physical therapy.
  • In its December 2013 issue, The New England Journal of Medicine reported that arthroscopic knee surgery for patients with degenerative meniscus tear and no osteoarthritis is no more helpful than a fake surgery.

In summary, if you’re middle-aged and develop knee pain, please don’t fall for the cursory knee exam, quick look at the knee MRI, and the conclusion that a meniscus tear seen on the image is the cause of your pain and needs to be surgically removed.

The upshot? An entire generation of physicians has been educated to look at an MRI or arthroscopy picture with great reverence and to deduce that any abnormalities seen there certainly are the cause of knee pain. In reality, knee pain is an incredibly complex thing that involves nerves, bone, and tendons, and the only thing on knee MRI that studies reliably can associate with knee pain is a finding that most physicians ignore—bone-marrow lesions. Cartilage loss and meniscus tears, despite a medical community that’s hyper-focused on them, likely mean much less than once was thought.


“Why Middle-Aged People Should Ignore Cartilage Loss” first appeared as a post on the Regenexx blog.
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