Medical myths are ideas held by physicians—and consequently by patients—about a variety of conditions. When subjected to medical research, however, these myths turn out to be false. A big whopper that’s widely believed is that lost knee cartilage causes pain.

Cartilage cushions bone joints. Loss of cartilage from a joint accompanies arthritis. Nearly all physicians and patients believe that cartilage loss is directly related to pain, and so if a patient has a large amount of cartilage loss, that patient also experiences a large amount of pain. It’s for this reason that patients generally are fixated on learning details about their knee cartilage. Is it good? Is it bad? How much is there? Is there a hole in it? What if the research of the last five years actually showed this concept to be a medical myth? How would this change orthopedic care?

Two large, ongoing studies—the Framingham Osteoarthritis Study and another by the Osteoarthritis Initiative—are tracking patients with osteoarthritis in their knees. Both studies are sponsored by the National Institutes of Health and make use physical examinations, X-rays, MRIs, blood work, questionnaires and biomarkers.

So what do these huge studies say about knee cartilage loss and pain? Are they associated? Does lost cartilage = pain? An analysis of the Framingham data shows that among more than 700 patients, the loss of cartilage seen on MRIs was not associated with pain. Another study from that same data set showed that not only was cartilage loss not associated with pain, almost all of the “abnormalities” on a knee MRI that would prompt surgeons to operate also were not associated with pain. An analysis of data from the Osteoarthritis Initiative shows that despite looking at cartilage loss in almost 500 patients, the amount of lost knee cartilage visible on X-ray and MRI was not strongly associated with pain. The conclusions of these large studies to date indicate that lost cartilage in the knee is not associated with knee pain or with lost function.

What does this suggest? A patient whose doctor glances at a knee X-ray and/or MRI and determines that lost cartilage is the cause of knee pain is relying on a medical myth and not science. Knee pain is caused by a complex interplay of factors, only a handful of which can be seen on MRI. Reduced amounts of cartilage is not one of those factors.

“Orthopedic Urban Myths: Lost Cartilage Equals Pain” first appeared as a post on the Regenexx blog.