Special tests for FAI - the truth about FADIR and FABER and other hip impingement tests

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 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:

• MRI shows labral tears and the cam and/or pincer bone shapes 
• 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, read this article.

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 hip pain 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). 

We work with a lot of clients who have been told they have hip impingement, otherwise known as femoroacetabular impingement (FAI). We’ve seen people with this diagnosis improve their hip function without surgery, and this has made us look deeper into the diagnosis.

In this article, we’re going to look at the FADIR and FABER tests.  

FADIR - the big hip impingement test

The FADIR test is one of several tests doctors use to arrive at the hip impingement diagnosis. But how useful is it really?

FADIR stands for “Flexion - ADduction - Internal Rotation.” It’s also known as “anterior hip impingement test.” Theoretically, if this test is painful, you have FAI. That sequence of movements smashes the labrum and causes pain. 

There’s a catch, though. We have multiple muscles that attach in the groin and can easily be smashed, pinched, overworked, or just plain annoyed — to speak NOTHING of a labrum. That sequence of movements can trigger pain from muscles as well.

The science is clear: your FADIR test results may have no link to having a labral tear or femoroacetabular impingement bone shapes.  While that may seem like a big claim, it's based on findings in high quality research studies for shoulders and the spine.

You can have a labrum tear in your shoulder, and it won’t necessarily cause you pain. The same is true in the hip. You can have labral tears and NO pain whatsoever. The science is very clear on that.

However, in a medical setting, if you have a hip labral tear and/or abnormal bone shape AND a positive FADIR, doctors will claim you are the perfect candidate for hip surgery.

What the hip impingement study on FADIR actually found

Here’s how they started: they gathered 34 athletes with groin pain (inner thigh near the pubic bone). A group of clinicians assessed them on ROM tests. Another group of clinicians assessed their X-rays for signs of FAI.

KEY POINT

The people with the “worst” FAI bone shapes didn’t even have pain on the FADIR test!

From the total of 68 hip joints, 64 (94% of them!) had X-rays with indications of FAI. All these athletes with groin pain must have FAI, right? The X-rays show it. So they will fail FADIR.

Wrong.

Only nine hips tested positive for the FADIR test. There was no relationship with the number of radiological signs. Similarly, there was no correlation between hip ROM and the number of radiological signs.

More simply: FADIR didn’t have anything to do with the presence of FAI bone shapes. Even more simply: FADIR was pointless.

Quoting the study:

(...) There was no association between the number of radiological signs and the anterior hip impingement test being positive. In fact, the two hips with the highest number of radiological signs of FAI had a negative anterior hip impingement test.

So what does that all mean?

There was no link between FADIR and FAI bone shapes. Zip. Zero.

The people with the “worst” FAI bone shapes didn’t even have pain on the FADIR test. 

Can FADIR predict hip impingement?

Another study published in the Journal of Science and Medicine in Sport in 2018 takes a look at the FADIR test as well.

These researchers wanted to know if the FADIR could detect "abnormal" FAI bone shapes. They compared the FADIR outcomes to MRI’s from 74 youth male ice hockey players. 

The athletes had ages between 13-20 years old. They had an average playing experience of 11 ± 2 years. None of them had any hip diagnosis or previous hip surgery. These players did not have hip pain.

The idea behind this study was that if the FADIR produces pain, the player should have FAI signs on the MRI.

Wait, why use young ice hockey players for this FAI study?

Surgeons have long pushed the idea that hockey players have hip impingement in high numbers. The prevalence of cam morphology is reported to range between 45% and 75% in ice hockey players. (Note: this is actually not any higher than in the general population, but surgeons don’t talk about that).

Hockey is a high impact, highly demanding sport for the hips. Surgeons claim this overload can allegedly produce a femoral-bone adaptation, i.e. cam morphology.

So young ice hockey players are supposedly at high risk for developing FAI symptoms as a result of these bone shapes.

How accurate was the FADIR test for hockey players?

Well, from those 74 hockey players:

• Only 7 had a positive FADIR and an abnormal shape shown in the MRI. The test could predict only 7 out of 74. That's 7 true positives.

• 30 had a positive FADIR and a normal bone shape. That's 30 false positives.

• 10 had MRI findings of abnormal shape, but no pain with the FADIR. The test failed to predict 10 abnormal shapes. That's 10 false negatives.
  
  
• 27 didn’t have pain with the FADIR and had a normal bone shape. That's 27 true negatives.

WOULD YOU TRUST THIS TEST?

The FADIR had a 40% false positive rate. And it was only able to accurately identify FAI bone shapes 9% of the time.

There was zero link between the bone shapes and pain on this test.

To highlight the most salient point, the FADIR test had a 40% false positive rate. And a 9% true positive rate. That means FADIR is totally useless in identifying "abnormal" bone shapes. It also demonstrates that the FAI bone shapes are NOT linked to pain! 

Put another away: you can have the FAI bone shapes, no hip pain, and have no pain on the FADIR. That means the bone shapes are irrelevant AND the test is pointless. Using a test like this to convince someone to get surgery is misguided at best and irresponsible at worst.

Bottom line: is the FADIR test reliable for hip impingement?

Short answer: FADIR is NOT reliable as a hip impingement test. If doctors and therapists want to act on the best available evidence they should abandon this as a clinical tool. 

From the first study:

Radiological findings of hip impingement are often present without the anterior hip impingement test being painful. The anterior hip impingement test may not be specific for femoroacetabular impingement. Clear diagnostic criteria for femoroacetabular impingement and other causes of groin pain are needed.

Translation: Having FAI bone shapes has no relationship to a positive or negative FADIR test. It's NOT reliable for diagnosing hip impingement.

From the second study: 

The FADIR test is inadequate for screening cam and pincer morphology in youth ice hockey players without diagnosed hip disorders (...). Future studies should investigate the accuracy of other hip examination tests (...).

Translation: FADIR isn’t reliable for predicting abnormal bone shapes. It’s not reliable for diagnosing hip impingement. When you look deeper, you discover that NONE of the tests for hip impingement work - and that there’s very little evidence for the entire theory!

In the end, we’re left with a lot of medical tests and images that create the illusion of the need for surgery.

What about the FABER test for identifying hip pain problems?

Now you might be thinking, "okay, the FADIR test is apparently not good. But I bet the FABER is good. That's why doctors use both to examine the cause of hip pain for their patients!" 

So maybe the Flexion Abduction External Rotation hip pain test might be more accurate, thus giving us a fuller and more accurate picture of the cause of someone's hip pain! 

Unfortunately that's not the case. 

In a 2010 study looking at the validity of hip pain tests, researchers found that the FABER test had a specificity of only 25%. 

Let's translate that into English. 

If you performed the FABER test on 100 people who DID NOT have a structural deformity of any kind, the FABER test would only identify 25 of them as having no structural deformity.

75 of people would be inaccurately identified as having a structural deformity. 

Read that again. 

THE FABER TEST HAS A VERY HIGH RISK OF FALSE POSITIVES. 

What if you use FADIR and FABER hip pain tests together?

Doctors will commonly assert that the inaccuracy of these tests can be overcome by using multiple tests. In other words, if one test is inaccurate, you can use multiple tests to improve the accuracy and certainty of your diagnosis. 

That's not the case. 

In fact, the same 2010 study by Maslowski et al found that by combining inaccurate tests, you increase the false positive rate to 100%. 

When it comes to diagnosis hip pain, that is the exact scenario playing out in doctors' office all over the world! 

How to beat hip pain from a non-medical perspective

Tread carefully. The medical model of hip pain drives people toward injections, reduced activity, and eventual surgery. This tendency is driven by surgeons' biases and is not backed by evidence. 

The real answer is to learn how to retrain your muscles for proper motion and function. That is the simplest, least invasive, and natural means to reclaiming your life. 

The challenge in this approach is that it requires lifestyle changes and reprioritizing exercise and movement over sitting on chairs and staring at screens. It may also mean giving up certain hobbies and athletic endeavors for a long period as you retrain your body into long-forgotten and disused movement patterns. 

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.