Bias in early femoroacetabular impingement research

I’ve been doing a lot of digging and reading lately, so I wanted to share some quick findings in terms of bias in the early FAI research.


The early research was done by a very small number of orthopedic surgeons who were looking only at bones and the structures within the hip joint for an explanation for pain and movement problems.

A few surgeons had perfected a new technique of dislocating the hip joint so that the insides of the joint could be examined (something that could not be done before). This provided a view into the joint that they believed could show small abnormalities that they believed would explain arthritis and hip pain. They published a paper on their new technique and proposed that this new technique could help identify FAI morphology as a cause for hip arthritis.

Of the top 8 studies cited in the research and discussion of femoroacetabular impingement these same surgeons were involved multiple times in providing purported evidence of this theory. In the top 8 studies, Reinhold Ganz, MD; Michael Leunig, MD; Javad Parvizi, MD; Martin Beck, MD; and Klaus Siebenrock, MD appear several times each.

fai researcher citations

While it is not necessarily problematic that experts are researching a topic of interest, these articles and studies cite their own research articles as evidence supporting their own assertions. That is extremely problematic.

Imagine if I told you that I believed I had a new way of understanding and curing cancer. I publish one article. A friend and I publish another article citing the first article as proof of my theory. Two other friends and I publish a third article citing the first two articles. A group of all of us then publish another article citing our first three articles as evidence of the strength of our argument.

This would not be considered sound science nor would my theory be particularly convincing once you realized that I was citing my own theory as proof of my own theory.

With only a handful of surgeons examining the problem and with all of them looking at a bone-based theory of hip pain, an academic echo chamber was created. Bone was the only thing to study as a cause of hip pain.

This is also unfortunate for patients, as many people assume that orthopedic physicians are seriously considering muscle as a potential problem when – especially in this case – they do not seem to be.

Many people also believe that muscular causes of hip pain are ruled out by good physical therapy. However, hip pain research has been driven by the orthopedic surgery community, so the conclusions almost always support a bone-based theory and surgical intervention.

Physical therapy as a whole has accepted the orthopedic description of hip pain and femoroacetabular impingement as a bone issue. Operating on that assumption, physical therapy of any variety is logically considered hopeless.

As a result, there have been few attempts to correct dysfunction in a research environment. This belief makes it unlikely that conventional physical therapy approaches will produce satisfying results.


About the Author

Matt Hsu is a trainer and orthopedic massage therapist. He fought a long battle with chronic pain all over his body and won. He blends the principles he learned in his journey, empirical observations with clients, and relevant research to help others get their lives back.