What’s the True Link Between FAI Bone Shapes, Hip Pain, and Hip Arthritis?
Conventional FAI Orthopedic Theory Comes Up Short on How Bone Shapes Affect Hip Pain, Arthritis, and Movement. Diagnostic Scans and Studies Tell a More Accurate Story.
If you’ve been diagnosed with femoroacetabular impingement (FAI), doctors almost certainly blamed your hip pain on the shape of your bones.
The orthopedic theory of FAI claims that people with abnormal bone shapes get hip pain, have movement problems, develop hip osteoarthritis (OA), and have hip labral tears.
Doctors often make these claims — despite a large body of strong evidence showing that bone shapes are NOT the reason hips hurt.
If this FAI theory were accurate, certain observations and predictions would hold. But they don’t.
What Does Science Show about FAI Bone Shapes Causing Hip Pain?
“The bad bone shapes of FAI clearly cause hip pain.” Nearly every physician you meet when you have hip pain will repeat this to you. Scores of reputable health websites say it too.
If conventional FAI theory were true, we should be able to look at x-rays, CT scans, or MRIs to identify bad bone shapes in people having pain and movement issues. A person with cam and/or pincer bone shapes should have hip pain or movement restrictions. Yet they don’t.
What’s more, signs of “impingement” in diagnostic imaging scans are very common in the asymptomatic population, casting even more doubt on claims that bone shapes alone are responsible for the symptoms of hip pain and movement problems.
Let’s pull back the curtain and take a look at what medical studies have been finding for years.
Researchers in 2008 looked at 4,151 people in the Copenhagen Osteoarthritis Study. About 17 percent of the men and 4 percent of the women had cam deformity. If FAI theory were true, there should have been a clear relationship between the presence of bad bone shapes and hip problems. But there wasn’t.
Researchers found that cam deformity was common and completely unrelated to the development of hip pain and arthritis. In the researchers’ words: “The distribution of cam deformity was unaltered in subjects with normal joint-space width or other features of hip-joint degeneration.” Also: “We found no significant association with self-reported hip pain … It is a far from uncommon deformity in subjects with no apparent evidence of hip-joint osteoarthritis.”
In plain English, this means that the cam deformity had nothing to do with joint-space problems. It had nothing to do with hip pain. And it had nothing to do with arthritis of the hip.
Was this a fluke? Seems not.
Two years later, researchers published a study looking at bad bone shapes, FAI, and hip pain. They looked at 200 asymptomatic (no hip pain) volunteers and discovered 24.7 percent of men and 5.4 percent of women had bad bone shapes despite being symptom-free.
Then in 2011, yet another study that looked at pelvic CT scans for 108 men and 272 women found that 14 percent of the men and 6 percent of the women had the irregular bone shapes — but no complaints about their hips! In the researchers’ words: “It appears that the cam-type femoroacetabular deformity is not rare among the asymptomatic population.” So, many people likely have femoroacetabular deformity, but it doesn’t cause them pain or problems. It’s worth noting that an additional 15 percent of men and 6 percent of women in the study had “borderline” bone irregularity without any complaints.
And in 2013, a study looked at the CT scans of 50 asymptomatic people aged 20 to 40. Their findings also were telling: “At least one abnormal parameter was present in 66% of joints, and two or more abnormal parameters were present in 29% of joints … Parameters of mixed morphologic characteristics (cam and pincer) were found in 22% of joints.”
FAI Bone Shapes and Pain: The Bottom Line
The message is clear: Alleged “bad,” “abnormal,” and “malformed” bone shapes are not correlated with hip pain. You can often find these bone shapes in symptom-free people. Therefore, you cannot look at diagnostic scans and declare: “That bony overgrowth is causing your hip pain!”
Equally important: What surgeons call “bad,” “abnormal” or “malformed” is actually quite normal. Based on this evidence, we shouldn’t use the word “deformity” when we see cam and pincer bone shapes. They are simply normal anatomical variations.
FAI and Arthritis: Scrutinizing Orthopedic Theory
The current theory of FAI and pain is that malformed bones lead to degenerative changes in the hip joint, resulting in pain and discomfort. That means even if young people with these bone shapes have no symptoms, they likely will as they get older because those shapes lead to osteoarthritis (OA) later in life, as joints wear down with age and use.
There’s a major hole in this theory: FAI has NOT been shown to lead to arthritis.
FAI Is Not a Precursor to Arthritis
If FAI bone shapes eventually lead to arthritis and joint damage, it would certainly make sense to try to fix the bone shapes as soon as we spot them. But studies show they don’t.
In 2011, researchers published a study where they looked at the long-term outcomes of patients with no hip problems but who had FAI bone shapes. They looked for any relationship between those bone shapes and the development of hip osteoarthritis.
They found no link. And their summary states it plainly: “We conclude that a substantial proportion of hips with femoroacetabular impingement may not develop osteoarthritis in the long-term. Accordingly, in the absence of symptoms, prophylactic surgical treatment is not warranted.”
Then in a 2015 study, researchers looked at 547 athletes with an average age of 67. None of the athletes had hip problems. Researchers evaluated them for signs of FAI, osteoarthritis, and hip dysplasia (another story altogether). They found a stunning 83 percent of the athletes had signs of FAI in their x-rays.
Their conclusion: “Radiographic findings consistent with FAI in these senior athletes were common and were not associated with the presence of OA. These data suggest that the need to screen for asymptomatic young athletes for radiographic evidence of FAI … may not be necessary.”
In other words, having the alleged bad bone shapes doesn’t lead to hip problems even when you’re a senior-aged athlete.
Think about this: The FAI bone shapes are present in young people in high numbers with no apparent ill effects. And a 67-year-old can have the FAI bone shapes his or her whole life and still suffer no ill effects.
That means the bone shapes are not related to hip pain when you’re a teenager or in your 20s. And the bone shapes don’t lead to hip degeneration or hip pain when you’re older. So now what reason would we have to fear the bone shapes?
The answer is that we don’t have a reason to fear the bone shapes. They are clearly not the cause of hip degeneration for the young or old. This completely undermines hip surgeons’ theories about hip pain and bad bone shapes.
A Self-empowering Strategy that Works: the FAI Fix
If FAI bone shapes, arthritis, and pain aren't related, it makes sense to put our attention on something other than bones.
What else is there? Muscles and movement.
Hip impingement is a problem that shows itself generally with movement, and movement requires muscles. You want to move your muscles properly in order to move your bones safely and without pain. Even something as simple as sitting requires healthy muscle activity for you to feel comfortable, capable, and confident.
The FAI Fix is designed to help you focus on strategies that help you retrain muscles for better hip-joint function — regardless of what studies or diagnostic scans show.
What about success rates for surgery for hip impingement? Read: Can Surgery Guarantee Improvement for FAI?