Is femoroacetabular impingement something to worry about?

A while back, I started looking into femoroacetabular impingement because I started reading about it and hearing about in hockey circles. When I started hearing what the symptoms were, I realized, “HEY! I had those problems! But I’ve managed to get out of those problems with proper stretching and very careful strength training…

I wrote a few blog posts and made a video on YouTube that talked about why FAI doesn’t make sense to me.

I laid many reasons why I thought the entire explanation seemed shoddy which I’ll summarize here:

  • The current FAI explanation blames bone shape (morphology) for labral tears, pain, and future arthritis
  • The diagnosis relies on diagnostic imaging (x-ray, MRI, CT scan) to find a “cause” for movement impairments and pain
  • There have been countless times in recent medical history in which blaming defects that show up in diagnostic imaging has turned out to be totally baseless and the result of biased and/or flawed research (see: spinal surgeries for back pain, meniscectomies for knee pain, labral tears in shoulders)

I’ve since made many, many more videos and even co-created The FAI Fix to show people how to address the muscular issues that contribute to what is currently called “FAI.” I want you to keep reading, so I’ll give you a link at the end to look at.

I want to be clear. I don’t think bone shapes cause the pain. I think “FAI” is a convenient name for hip movement issues, but it makes no sense to blame bone shapes for impaired movement patterns until you’ve first looked at the things that very obviously affect movement patterns: muscles.

I’ve been looking at as much recent research as I can find to see what quality studies on FAI are finding. I came across two today that you should read if you’d like to understand my skepticism a bit more.


The first is one done in Chile…

Hip Morphology Characterization: Implications in Femoroacetabular Impingement in a Chilean Population.

RESULTS: We studied 101 subjects (202 hips) with a mean age of 36.8 ± 14.4 years. The mean center-edge angle was 39.4° ± 7.2°. The crossover sign was present in 34 cases (33.7%). The mean alpha angle was 49.7° ± 8.3°. Depending on the cut points chosen for FAI-related parameters, between 39.6% and 69.3% of an asymptomatic Chilean population were found to have morphological features related to FAI.

CONCLUSION: Our findings suggest that the proposed pathological threshold values in the literature cannot be extrapolated to a Chilean population, and this must be taken into consideration when evaluating Latin American patients with hip pain.

Why is this important? Because it shows that in Chile, between 39.6%-69.3% of the ASYMPTOMATIC POPULATION has the FAI bone shapes. The rather conservative conclusion of this study is that the parameters set for diagnosing FAI don’t make sense when looking at only Chileans.

You may be scratching your head now. What is it about Chileans that’s so different from Americans? Or Europeans? Are they not also human beings with similar biomechanical requirements?


Which brings us to the second study done at UC San Francisco…

Femoroacetabular Impingement: Prevalent and Often Asymptomatic in Older Men: The Osteoporotic Fractures in Men Study.

METHODS: Anteroposterior radiographs were obtained in 4140 subjects (mean age±SD, 77±5 years) from the Osteoporotic Fractures in Men study. We assessed each hip for cam, pincer, and mixed FAI types using validated radiographic definitions. Both intra- and interobserver reproducibility were >0.9. Radiographic hip OA was assessed by an expert reader (intraobserver reproducibility, 0.7-0.8) using validated methods, and summary grades of 2 or greater (on a scale from 0 to 4) were used to define radiographic hip OA. Covariates including hip pain in the last 30 days were collected by questionnaires that were answered by all patients included in this report. Logistic regressions with generalized estimating equations were performed to evaluate the association of radiographic features of FAI and arthrosis.

RESULTS:Pincer, cam, or mixed types of radiographic FAI had a prevalence of 57% (1748 of 3053), 29% (886 of 3053), and 14% (419 of 3053), respectively, in this group of older men. Both pincer and mixed types of FAI were associated with arthrosis but not with hip pain (odds ratio [OR], 1.63; 95% confidence interval [CI], 1.25-2.13; p<0.001 for pincer and OR, 2.49; 95% CI, 1.65-3.76; p<0.001 for mixed type). Patients with hips characterized by cam-type FAI had slightly reduced hip pain without the presence of arthrosis compared with hips without FAI (OR, 0.82; 95% CI, 0.68-0.99; p=0.037). A center-edge angle>39° and a caput-collum-diaphyseal angle<125° were associated with arthrosis (OR, 1.53; 95% CI, 1.22-1.94; p<0.001 and OR, 2.09; 95% CI, 1.24-3.51; p=0.006, respectively), but not with hip pain (OR, 0.89; 95% CI, 0.77-1.03; p<0.108 and OR, 0.99; 95% CI, 0.67-1.45; p=0.945, respectively). An impingement angle<70° was associated with less hip pain compared with hips with an impingement angle≥70° (OR, 0.76; 95% CI, 0.61-0.95; p=0.015).

CONCLUSIONS: FAI is common in older men and represents more of an anatomic variant rather than a symptomatic disease. This finding should raise questions on how age, activities, and this anatomic variant each contribute to result in symptomatic disease.

I added the bold to the conclusions section because it is so crucial. As shown by many other large scale studies on FAI, there does not appear to be any causal relationship between FAI bone shapes and actual symptoms.

There are some who argue that it’s possible to have FAI morphology and no symptoms and that perhaps the bone shapes are an early indicator of coming disability. This is not a logical conclusion, especially based on studies like this one.

Here you have thousands of older adults with a mean age in the mid 70s with very high incidences of FAI morphology and with absolutely zero correlation with pain. Surely if the FAI bone shapes were going to cause pain and arthritis, it would show up by the mid 70s.

If FAI bone morphology truly is the cause of pain and disability, we should see a very clear correlation between FAI bone shapes and the presence of symptoms. We don’t. And as such, it’s not the bone shapes we should worry about but rather the tangle of muscles that help control function of the hip joint.

My buddy Shane and I created the FAI Fix to show you what we’ve done on ourselves and what we’ve seen work for the clients we’ve trained and worked with in person and around the world. If you’re looking for a way to retrain your hips so you can avoid or recover from a disappointing surgery, check it out.

FAI fix cover



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.