Special Tests for Femoroacetabular Impingement (FAI) are medically misleading

If you have hip pain, and you've been told you have femoroacetabular impingement (FAI), you may have had a series of movement tests (called "special tests" in medical jargon) done to confirm your diagnosis.

If you have hip pain and are wondering if you there are good tests for femoroacetabular impingement that will tell you if you have FAI, you may found a number of common tests that are believed to be reliable.

In either case, this article is going to cover something medical literature on FAI overlooks: the tests for hip pain causes are wildly unreliable. 

What are special tests for femoroacetabular impingement?

A special test for FAI is simply a movement that doctors believe demonstrates that hip bone shape is responsible for your pain.

If a movement produces pain, it's a "positive" sign that you have the condition known as FAI. If a movement does NOT produce pain, it's a "negative" sign.

One of the most well-known is the FABER test.

There are a number of other well-known tests to confirm whether or not you have FAI, and they are often used in conjunction with one another and with MRIs and X-rays to determine if you have femoroacetabular impingement or not.

In current medical practice, the diagnostic process for femoroacetabular impingement relies on:

  1. MRI shows labral tears and the cam and/or pincer bone shapes 
  2. Special tests produce pain (i.e. are positive).

There are major issues with both of these components. In this article, we're going to focus only on the special tests.

If you're interested in learning more about the problems with MRIs and femoroacetabular impingement, you'll find this video helpful - and this one too.

What's the problem with special tests for femoroacetabular impingement?

With any medical test, there are four categories of result we want to pay attention to: true positives, true negatives, false positives, and false negatives. 

True positives and true negatives are great! Ideally our tests should catch all the cases of a disease and identify all the cases where a disease is NOT present.

High rates of false positives and false negatives make a test less useful and less reliable.

In the special tests for hip pain and femoroacetabular impingement, the problem is that the tests have extremely high false positive rates. 

For example, researchers used the anterior hip impingement test and X-rays to see how well these results correlated with one another and with actual hip problems. They found no strong correlations between bone shapes, the hip impingement test, and hip pain.  You could have a positive sign of hip impingement but no X-ray evidence of FAI. Also, you could have negative test and HAVE an X-ray sign of FAI.

The test results just didn't match up to anything. 

All the currently performed hip special tests have very high false positive rates, so you're likely to be told you have femoroacetabular impingement - whether you have it or not (and whether it matters or not). 

Are false positives with tests for femoroacetabular impingement a problem in the real world​​​​?

Commenters in the medical community will suggest that performing multiple special tests to rule in or rule out FAI increases the accuracy of the result. 

But this isn't the case.

In one research study done in 2010, researchers found that the BEST test in terms finding true negatives was only able to identify them 32% of the time. That means if you did NOT have some kind of hip joint problem in an MRI, the test would still say you had a problem.  

Incidentally, this top-performing test is one that is not even regularly used these days.

The other three tests had WORSE true negative/false positive accuracy (to see these numbers, you'll need to get the full text of the study).

They further discovered that if  they combined multiple tests tests together (four of them in this study), the  rate of false positives went up to 100% (again, to see this, you need to read the full text as the authors chose to exclude this key data from the abstract).

That means if you go in with NO femoroacetabular impingement bone shapes or labral tears (or whatever other alleged deformity), combining these four tests guarantees that you'll get a positive sign that indicates that you have a hip joint problem.  

That's not good sense. And that's not good medicine. 

In the real world, people with hip pain undergo X-rays, MRIs, and multiple special tests to confirm or deny "FAI." 

The unacknowledged problem, however, is that combining these tests and interpreting them in the conventional manner virtually guarantees a diagnosis of "femoroacetabular impingement" or some other structural problem (like a labral tear). 

Final thoughts on special tests for femoroactabular impingement

It's important to note that FAI is a very new diagnosis historically speaking.

The ideas about the tests are based off of very, very limited research.

And when you dig beyond the abstracts and their surface-level summaries, you find that the data around femoroacetabular impingement points very strongly in one direction: bone shapes don't matter. The medical community is barking up the wrong tree.

The tests don't match up to symptoms, and the treatment (surgery) is not as successful as surgeons initially believed.

That's why we believe that looking at muscle function, retraining proper movement, and gradually restoring range of motion and control is the healthier, natural solution to hip pain in the 21st century.

Learn more about our DIY program to help you train out of hip pain.


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.