Evidence doesn’t equal symptoms. Get the picture?

The sports medicine industry is lately taking a hard look at the reliance on imaging for diagnosis, as well they should. Diagnostic imaging has become a multi-billion dollar industry in the United States(1). The dependence on imaging for clinical decision making decreases the amount of time the practitioners spend with patients and possibly the number of referrals for conservative management.

As discussed in a recent newsletter, two-thirds of the knees in asymptomatic middle-aged runners show evidence of some sort of pathology on magnetic resonance imaging (MRI)(2). This ‘damage’ existed before the previously sedentary subjects even started training for a marathon. Oddly enough, the images taken after completing the training and the subsequent race weren’t significantly worse than the pre-training images; some even showed improvement.

A multi-center systematic review and meta-analysis seems to point toward the same conclusions. This study looked for evidence of osteoarthritis (OA) on MRIs of asymptomatic adult knees(1). They evaluated 46 cross-sectional and 17 longitudinal studies with a total of 5397 knees. The investigators found that the incidence of OA increased substantially in subjects over 40 years old and, therefore, reported the results in an under and over 40 years of age format (see table 1).

Table 1: Incidence of osteoarthritis in asymptomatic knees

Degenerative changeIncidence in population < 40 years old Incidence in population ≥ 40 years old Is increase in ≥ 40 population significant?
Articular cartilage defect11% 43%YesOccurred more often in women.
Meniscal tears4%19%YesOccurred more often in women.
Medial tears significantly more common than lateral.
Bone marrow lesions14%21%NoNot associated with gender.
Higher incidence in <40 year old former weight bearing athletes.
Osteophytes8%37%YesNot associated with gender

This systemic review showed that degenerative changes in the knee are present in nearly half of the asymptomatic population over 40-years-old. It also revealed that former weight-bearing athletes under 40 have a higher incidence of bone marrow lesions, yet they don’t complain of knee pain. Therefore, when clinicians recommend procedures based on MRI reports, they run the risk of having identified a red herring. As these studies show, evidence of OA in the knee does not necessarily correlate with symptomology. Could it be that weakness, inactivity, overweight, or inflammation from another source is the cause of the pain? Another possible trigger is under or overloading the joint.

So why the reliance on imaging? When did practitioners begin to doubt their clinical skills and judgment? At least in the United States, it was likely when insurance companies wanted proof. Imaging studies are ordered to validate medical diagnosis and decision making. However, they have not significantly improved the treatment outcomes in those with knee pain(1).

It’s time to return to sound clinical skills and the utilization of basic exercise physiology. While joint deterioration doesn’t always cause symptoms, a patient can’t un-see an MRI. Does seeing an image of cartilage damage and hearing the descriptor ‘bone on bone’ make a knee more symptomatic? More research needs to determine if knowing MRI results changes the outcomes of treatment choices and conservative management.


  1. Br J Sports Med. 2019;53:1268-78
  2. BMJ Open Sp Ex Med. 2019;5:e000586
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