Imagine this for a moment. You're active, maybe
really dedicated to a sport, perhaps football,
running, dance, whatever it is, or maybe you
just love being active. And then, this ache starts,
deep in your hip, maybe you're groin, not from
a specific injury, it just creeps up. Sometimes
it's sharp, especially after activity or even
just sitting for a while. It's a very common
story, unfortunately. And you live with it for
months, maybe years, adjusting how you move,
hoping it'll go away. but it often doesn't. Well,
that nagging pain, that mechanical niggle might
be femurocetabular impingement or FAI. Indeed.
It affects a huge number of symptomatic athletes,
maybe 55%. But it's also present, often silently,
in about 10, 15 % of the general adult population.
Today, we're diving deep into FAI. I'm your host,
here to navigate through the complex details,
and I'm joined by our expert, Jest. He has this
fantastic ability to take really complex medical
information, see the patterns, and explain it
all in a way that makes sense. It's great to
be here. The hip joint really is an incredible
structure, designed for both power and subtle
movement. But yeah. even small changes in its
shape can cause significant problems like FAI.
Absolutely. And that's our mission today to really
get under the skin of femurocetabular impingement.
We'll look at what it is, the different types,
who gets it, why they get it, and crucially,
how it's diagnosed and what the latest treatment
options look like from physio right through to
surgery and what it all means for long term hip
health. So let's get stuck in. OK, let's start
right at the beginning. Femoral acetabular impingement,
FAI. What exactly is it? It doesn't sound like
a typical disease, does it? More like a physical
fit issue. That's a very good way to put it,
actually. It's not a disease like an infection.
It's what we call a pathomechanical process.
It's half a mechanical, right? Yeah. Think of
your hip as a near -perfect ball and socket joint.
You have the femoral head, the ball at the top
of your thigh bone, fitting snugly into the acetabulum,
which is the socket in your pelvis. Normally,
they glide smoothly. In FAI, that smooth gliding
is disrupted. You get abnormal contact, basically.
The femur and the acetabulum repeatedly collide
or rub against each other incorrectly during
movement. A collision. Exactly, a mechanical
collision. And this isn't gentle. It's often
a forceful pinching or grinding. Over time, this
constant abnormal contact starts to cause damage.
Damage to what, specifically? Well, typically
the first structure to suffer is the labrum.
That's a ring of strong fiber cartilage around
the rim of the socket. Right. Think of it like
a gasket or a seal. Okay. the rubbing damages
it, causes tears, then the articular cartilage,
that incredibly smooth white lining in the bone
surfaces that lets them glide, that gets injured
too. Right, the slippery stuff. Precisely. And
this ongoing damage, this mechanical insult,
is what leads to the progressive hip pain and
stiffness that people experience. So yes, fundamentally,
it's a problem of shape and mechanics. That makes
sense. And you mentioned different types, that
this extra bone or abnormal shape shows up in
distinct ways. That's right. Although the underlying
issue is this abnormal bone shape causing the
collision, where that abnormality is located,
defines the type, and often correlates with who
tends to get it. We generally talk about two
main types, though very often people have a mix
of both. OK. The first is cam impingement. The
name comes from engineering, like a camshaft
that isn't perfectly round. Ah, OK. This is a
femoral based disorder. The problem is on the
ball side, the femur. We tend to see this more
in young athletic males. Young men, okay. Yes.
Essentially, the femoral head, or usually the
junction between the head and the neck, isn't
perfectly spherical. It's a bit aspherical or
too broad, often with a characteristic bump on
the front outer side. A bump on the ball. Exactly.
We're talking about a decreased head -to -neck
ratio or offset. Basically, the smooth contour
is lost. Now imagine this non -spherical ball
trying to move fully within the socket. It's
gonna jam, isn't it? Precisely. As a hip flexes
and rotates inwards, that bump, the cam lesion,
effectively levers against the rim of the socket.
This creates a shearing force right where the
cartilage meets the labrum. Ouch. Yes. Instead
of gliding, it peels the cartilage away from
the bone that's cartilage delamination, and it
can tear the labrum, causing labral separation.
On x -rays, you might see what's called a pistol
grip deformity because of the shape. Pistol grip.
Got it. So that's cam. What's the other type?
The second type is pincer impingement. This is
an acetabular -based disorder. The issue lies
with the socket, the acetabular. So the socket's
the problem this time. Correct. We tend to see
this more frequently in active middle -aged women.
Here, the socket rim has too much coverage, an
overhang, usually at the front and top part.
Too much socket. In effect, yes. It might be
because the socket itself is angled slightly
backwards, it's acetabular retroversion, or it
might be just generally too deep, what we call
acetabular protrusia or coxoprofinda. So with
pincer, when the hip flexes, instead of the bump
shearing things, the overhanging rim of the socket
directly pinches or crushes the labrum against
the femoral neck. Crushing the seal. Exactly.
This often causes tearing within the substance
of the labrum itself. And interestingly, You
can get what's called a contracoup cartilage
injury. Contracoup? Like in head injuries? Similar
principle. As the front of the neck hits the
overhanging socket rim, it levers the back of
the femoral head against the back wall of the
socket, damaging the cartilage there opposite
the main impingement site. Wow. Okay. Any specific
signs on x -ray for pincer? A classic one, especially
with retroversion, is the crossover sign on a
pelvis x -ray. where the front and back walls
of the socket seemed to cross over. Right, CAM
and PINCER. But you said people often have both.
Yes, absolutely. It's really important to stress
that. Combined impingement, a mix of both CAM
and PINCER features, is actually the most common
scenario we see in symptomatic patients, perhaps
up to 80 % of cases. So often, we need to address
both aspects surgically. OK. That's clear. These
aren't just minor anacomical quirks then. They
cause real mechanical problems. And it sounds
like this isn't just about the immediate pain
of that collision. It sets off a kind of chain
reaction, doesn't it? Leading to bigger problems
down the line. Precisely. That's the critical
thing to understand about the long -term picture.
The immediate pain is from the pinching and rubbing,
yes. But it's the chronic, repetitive nature
of that mechanical collision that does the real
damage over time. This constant friction, whether
it is shearing from a cam lesion or crushing
from a pincer, leads to progressive labral degeneration
and tears. The labrum just isn't designed to
withstand that kind of abuse, so it wears down
phrase tears. And the cartilage too. And the
cartilage, too. That smooth gliding surface suffers
significant cartilage damage. It might soften,
fray, develop blisters, or even full thickness
tears or flaps. And the trouble with articular
cartilage is its very limited ability to heal
itself. It doesn't repair well. Not really, no.
So over time, this relentless wear and tear transforms
localized damage into broader joint degeneration.
which is why FAI is now recognized as a major
known risk factor for the development of osteoarthritis
of the hip. Ah, so it leads to arthritis earlier.
It certainly seems to accelerate the process,
yes, leading to hip dysfunction and potentially
the need for hip replacement surgery much earlier
in life than we might otherwise expect. It's
a pathway from subtle shape difference to significant
joint failure, potentially. That's quite sobering.
So if these bone shapes are the root cause, what
causes them? Is it something you're born with?
Is it genetics, or does activity play a role?
You mentioned athletes. It's a really key question.
And the honest answer is we're still figuring
out all the details. But the current thinking
points towards a combination of factors. It's
rarely just one thing. Firstly, there does seem
to be a genetic predisposition. Research suggests
genetic factors may contribute. Specific small
variations in our DNA, things called SNPs, single
nucleotide polymorphisms, tiny genetic differences,
some. like variants in genes called GDF5, FRZB,
DI02, HOX9, have been linked to particular hip
shapes, both on the femur and socket side, and
also to an increased risk of developing osteoarthritis.
So your genes can literally shape your hip in
a way that makes FAI more likely. It seems that
way, yes. It sets the stage, potentially. Interesting.
And the athlete connection, does playing sport
cause it? That's the athlete paradox, as you
called it. We definitely see more FAI, particularly
the cam type in athletes. But, and this is really
crucial, exercise does not cause FAI in a normal
hip. Okay, that's important. Yes. The leading
theory is that during adolescence, when the bones
are still growing and developing, the increased
stress along the great plate of a hip from high
intensity sports, think repetitive deep flexion,
rotation, like in football, hockey, martial arts,
might trigger a sort of stress reaction. The
bone reacts to the stress? Exactly an increased
stress reaction bone formation the body adapts
by laying down more bone But in this area it
can result in that cam deformity that bump So
intense activity during those key growth years
and someone perhaps already predisposed might
lead to the shape forming So activity doesn't
cause it from scratch, but it can contribute
to the shape developing, or at least make an
existing shape symptomatic earlier. Precisely.
If you already have that subtle anatomical difference,
vigorous activity involving lots of hip movement
will provoke the impingement more often and more
forcefully, leading to symptoms sooner. It unmasks
the problem. Right. Are there other factors?
Childhood conditions? Yes, definitely. Childhood
influences are important. A history of slipped
capital femoral bypasses or SEFE is a major one.
That's where the ball part slips off the thigh
bone at the growth plate during childhood. Even
after it's fixed surgically, the residual shape
change, the deformity, can directly cause impingement
later in life. Other conditions like perthase
disease, which affects blood supply to the hip
in childhood, and hip dysplasia, where the socket
is too shallow, are also linked to a higher chance
of developing FAI. So it's often multifactorial.
Genetics, developmental stress, maybe previous
hip issues. OK, that makes sense. But then...
If these shapes are actually quite common, as
you said earlier, why do some people have terrible
symptoms while others with the same x -ray findings
feel Absolutely fine. It's confusing. It is confusing
and it's a huge area of research You're right.
The prevalence of the bone shapes is surprisingly
high We mentioned 10 15 percent in the general
population having the morphology But remember
that study the meta -analysis by Frank at all
They found cam deformity in 37 percent and pincer
deformity in a massive 67 percent of asymptomatic
volunteers people with no hip pain at all 67
percent Wow Exactly. So a huge number of people
are walking around with these FAI bone shapes
without any symptoms. The morphology itself doesn't
automatically equal pain. We also see those gender
differences in prevalence can more in men, pincer
more in women. But again, many are asymptomatic.
So what's the tipping point? Why do symptoms
start for some people? The general consensus
is that symptoms develop when the mechanical
collision finally starts causing significant
damage to the cartilage or the labrum. It's when
those soft tissues, which have nerve endings,
start to break down under the repetitive strain.
Ah, so it's the damage, not just the shape. Exactly.
The onset of pain, clicking stiffness that usually
signals that the pathological process is now
actively injuring the joint structures. And once
that happens, if the impingement continues, the
condition is likely to worsen. The damage progresses.
Having the shape is one thing. Having symptoms
means the joint is now suffering. Right. Which
brings us neatly to diagnosis. For someone with
that nagging hip or groin pain, what are the
telltale signs? How do doctors start to suspect
FAI specifically, given hip pain can be so vague?
It can be very vague, you're right. That's why
a careful history and a thorough physical exam
are absolutely paramount. What do patients typically
report? Usually a gradual onset of hip pain.
It's often not a sudden thing. The location is
most commonly deep in the groin area, but as
we said, it can radiate to the thigh, buttock,
outer hip, even the back. The C sign? Yes. Often
they'll use that characteristic C sign, cupping
their hand around the side in front of the hip
to show where it hurts. That's quite suggestive
of something inside the joint. Okay. And what
makes it worse? Classically, pain is exacerbated
by hip flexion and internal rotation. So activities
involving those movements, high intensity sports,
squatting, getting in and out of cars, driving,
even just sitting for prolonged periods. Makes
sense that position forces the joint together.
Exactly. They might also report mechanical hip
symptoms, things like clicking, catching, locking,
or a popping sensation. That strongly suggests
a labral tear is involved. And during the physical
exam, what are you looking for? We look for restricted
movement. Often there's limited hip flexion and
particularly limited internal rotation, especially
when the hip is flexed to 90 degrees. Sometimes
internal rotation is less than five degrees.
Wow, very restricted. Yes, and the key provocative
test is the anterior impingement test or FEI
or test. We gently flex the hip to 90 degrees.
bring it across the body slightly, adduction,
and then rotate it inwards. And if that hurts?
If that reproduces their specific pain, it's
a positive test. It's highly sensitive, positive
in about 88 % of patients with FAI. It really
hones in on that specific conflict zone. OK.
So history and exam give a strong suspicion.
Then comes imaging, presumably, to confirm it
and see the extent of the problem. Absolutely.
Imaging is essential to confirm the bony shapes
and, critically, to assess the state of the labrum
and cartilage. It completes the picture and guides
treatment. What imaging do you start with? We
always begin with radiographs, standard x -rays.
A specific set of views is needed. a standing
AP pelvis view, an AP view of the affected hip,
and a good lateral view of the hip. What do these
show? They allow us to assess the bone structure,
looking for those cam and pincer lesions. We
look for the pistol grip deformity for cam, signs
of over coverage, like the crossover sign for
pincer, or maybe a deep socket protrusio. And
you measure things on the x -rays? Yes. Precise
measurements are key. The alpha angle, usually
measured on a special lateral view, like a dun
or frog leg view, quantifies the cam deformity.
An angle over 50 -55 degrees is generally considered
abnormal. We also measure acetabular coverage
with things like the lateral center edge angle.
An angle below 25 degrees might suggest dysplasia.
not enough coverage, which is different from
FAIs over coverage. Different views like the
done view are best for seeing the cam lesion,
while a false profile view helps assess coverage
at the front. So x -rays give the bony blueprint.
What about CT scans? CT scans can be a useful
adjunct. They give incredibly detailed views
of the structural abnormalities and allow for
amazing 3D reconstructions. These are fantastic
for preoperative planning, letting the surgeon
really visualize the shape and plan the bone
resection. The downside is the higher radiation
dose. Right. And for the soft tissues, the labrum
and cartilage. For that, MRI is the gold standard.
Specifically, MR arthrography is often preferred.
Arthrography. That involves an injection, doesn't
it? Yes, exactly. An intraarticular contrast
injection, a special dye, is put into the hip
joint just before the MRI scan. This dye leaks
into any tears or defects in the labrum or cartilage,
making them show up much more clearly. It's the
best modality to evaluate for articular cartilage
and labral damage. It makes sense. MRI also shows
the bone shape well, without radiation, and it's
excellent for ruling out other causes of hip
pain that might mimic FAI. like a vascular necrosis,
stress fractures, or various types of tendonitis.
So MRI is really comprehensive. Is there anything
else diagnostically? One other tool is a diagnostic
intraarticular injection of local anesthetic.
We numb the hip joint directly. If the patient's
pain significantly improves, even temporarily,
it strongly confirms the pain is coming from
inside the joint, likely the FAI. It can be very
helpful when the picture isn't perfectly clear.
That's a really thorough diagnostic process.
So once FAI is confirmed, surgery isn't automatically
the next step, is it? What about conservative
approaches? No, absolutely not. Non -surgical
management is always the first port of call,
especially for patients who are minimally symptomatic
or don't have those definite mechanical symptoms
like locking. What does that involve? It's usually
a combination approach. Firstly, activity modification.
This means identifying and reducing or temporarily
stopping activities that provoke the pain. Not
stopping everything, but being smarter about
movement. Avoiding the triggers. Exactly. Secondly,
and crucially, targeted physical therapy. A good
physio will assess movement patterns, look for
weaknesses or imbalances in the kinetic chain,
and work on improving hip range of motion and
strengthening the surrounding muscles, glutes,
core muscles. To support the joint better. Precisely.
Better control, better mechanics can sometimes
reduce the stress on the impingement zone. Thirdly,
pain management, mainly with NSAID's non -steroidal
anti -inflammatory drugs to reduce pain and inflammation.
Like ibuprofen. Yes. And as we mentioned that,
intraarticular injection of local anesthetic
and steroid can be used therapeutically too.
The steroid reduces inflammation inside the joint,
providing pain relief that can last weeks or
months, making physio more effective. But these
don't fix the underlying shape, do they? No,
and that's the critical limitation. Conservative
measures manage the symptoms, they manage the
inflammation, they might improve mechanics around
the problem, but they don't change the bone shape.
They don't stop the collision happening. So if
these don't provide... lasting relief. Then surgery
becomes the next consideration. If symptoms persist
despite a good trial of conservative management,
usually three to six months, or if mechanical
symptoms are prominent, then we discuss addressing
the underlying anatomy directly. Right. So tell
us about the surgical options. What's the aim?
The aim of surgery is to reshape the bones, the
femur, the acetabulum, or both, to eliminate
the abnormal contact, the impingement, basically
to restore normal hip mechanics and allow smooth,
pain -free movement. They're two main approaches.
The most common approach now is arthroscopic
osteoplasty. This is minimally invasive, done
through small keyhole incisions using a camera,
the arthroscoge, and specialized instruments.
Keyhole surgery for the hip. Exactly. The surgeon
can see inside the joint on a screen and precisely
trim the bony rim of the acetabulum, if it's
a pincer lesion, or shave down the bump on the
femoral head or neck for a cam lesion. That's
the osteoplasty part reshaping the bone. And
they can fix the labrum at the same time? Yes,
a huge advantage is that arthroscopy allows the
surgeon to thoroughly assess and repair or clean
out any damage to the labrum and articular cartilage
as well. Studies show it gives equivalent results
to open hip surgery, but often with a quicker
return to activity. That sounds promising. What's
the open surgery option? The alternative is open
surgical hip dislocation. This is the previous
gold standard. It involves a larger incision
and a technique where part of the hip bone, the
greater trochanter, is temporarily detached to
allow the surgeon to safely dislocate the hip
joint and get a wide direct view of the femoral
head and socket. Sounds quite major. It is a
bigger operation, yes, but it's designed very
carefully to preserve the blood supply to the
femoral head. So the risk of a vascular necrosis
or AVN is very low. It provides excellent exposure,
which can be really useful for significant femoral
deformity or complex cases. Return to play rates
for athletes after open surgery are historically
very high, over 85 -90%, provided they don't
already have significant arthritis. Okay, and
regardless of the approach, dealing with the
labrum is key, you said. Absolutely critical.
If there's a labral tear, which there usually
is in symptomatic FAI, it needs to be addressed
repaired or sometimes reconstructed at the same
time as the bone is reshaped. Just cleaning out
the labral tear, isolated labral debridement,
without fixing the underlying bony impingement
simply doesn't work long -term. Because the cause
is still there? Exactly. It's a major cause of
treatment failures. You have to address both
the bone shape and the soft tissue damage it's
caused. Right. Are there other surgeries sometimes
needed alongside? Occasionally, yes. If there's
significant hip dysplasia or etabular retroversion,
a more complex operation called a periocetabular
osteotomy might be needed to reorient the socket.
And if the joint is already badly worn out with
end -stage arthritis, then hip arthroplasty,
a total hip replacement, becomes the necessary
solution. It really depends on the individual
case. Okay. Now, surgery always carries risks.
What are the potential complications people should
be aware of with FAI surgery? And what's a realistic,
long -term outlook? That's a crucial conversation
to have with patients. While generally safe and
effective, complications can occur. What are
the main ones? Major, though thankfully rare,
complications include things like femoral neck
fracture, particularly during the bone reshaping
for a cam lesion. Surgeons are very careful to
limit how much bone they remove, generally less
than 30 % of the femoral neck diameter, to minimize
this risk. With arthroscopy, very rare risks
include things like abdominal compartment syndrome
from fluid leaking where it shouldn't, or nerve
injury. Other potential major issues, though
uncommon, are blood clots, DVTPE, deep infection,
or dislocation after surgery. A vascular necrosis
is a risk, though minimized by careful technique.
And minor complications. These are more common,
but usually manageable. Things like heterotopic
ossification where extra bone forms in the soft
tissues afterwards. We often give endocides like
endomethacin post -operatively to help prevent
this. Temporary nerve irritation or praxious
causing numbness maybe in the thigh or perineal
area from traction during arthroscopy can happen
but usually resolves. Superficial infection or
bruising are also possible. Okay and the long
-term prognosis. Does surgery stop arthritis?
That's the million dollar question, isn't it?
We know the natural history of untreated FAI
likely leads to early onset hip dysfunction and
arthritis. Surgery definitely needs to change
that course. It's very successful at reducing
symptoms and improving function in the short
to medium term, and it can prevent future damage
by stopping the impingement. But... The current
scientific evidence is still unclear whether
it will definitively delay or prevent the development
of hip arthritis in the very long run, say 15,
20 years or more. So it might still happen later.
It might. Patients need to understand that while
surgery aims for joint preservation and symptom
relief, they may still develop arthritis in the
future and potentially need a hip replacement
eventually. The goal is to push that possibility
as far down the road as possible. or lessen its
severity. That's important expectation setting.
And after surgery, rehab is vital, I imagine.
Absolutely essential. Post -operative rehabilitation
is just as important as the surgery itself. It's
a structured, progressive process guided by physical
therapists. What does it involve? It starts with
a period of protected weight -bearing, using
crutches for maybe... two to six weeks depending
on the surgery. Early passive range of motion
starts almost immediately to stop stiffness.
Then comes active range of motion followed by
intensive strengthening exercises for the hip
and core and gait training to normalize walking.
Getting back to sport. That comes later usually
after 12 weeks or so with gradual reintroduction
of jogging, jumping and agility exercises. It's
a careful progression tailored to the individual.
The physio's role is absolutely critical in guiding
this safely. It sounds like a long process. It
requires patience and commitment, definitely.
Finally, looking ahead, what's new in the world
of FAI? Where is the research heading? It's a
very active field. The number of scientific publications
on FAI has exploded in the last 15 -20 years.
We're seeing advancements like computer -based
navigation systems being developed to help surgeons
perform the bone resection even more accurately
during arthroscopy. Improving precision. Exactly.
But there's also an acknowledged need for more
high quality research. We need more mechanistic
studies to really understand why the damage occurs
at a cellular level. And critically, we need
more long -term outcome data studies following
patients for many, many years to truly understand
the natural course of FAI and the real long -term
impact of non -surgical and surgical treatment
on preventing arthritis. So still learning? Always
learning, yes. but we've come a very long way
in understanding and treating it effectively.
This has been incredibly informative. It really
drives home how complex hip pain can be stemming
from these underlying mechanical issues. Just
to summarize the key takeaways for everyone listening.
Firstly, FAI isn't just pain, it's a mechanical
clash in the hip caused by abnormal bone shapes,
cam, pincer, or usually combined. Bone hitting
bone where it shouldn't. Secondly, it's a clear
risk factor for developing early hip osteoarthritis,
especially in active people whose movements can
accelerate the wear and tear. Correct. Thirdly,
diagnosis hinges on specific clinical tests,
like that FADR impingement test, combined with
imaging x -rays for the bone shapes, MRI, often
with dye to see the laboring and cartilage damage.
Yes. Fourth, treatment starts conservatively
with activity changes and physio, but precise
surgery, often keyhole arthroscopy, can reshape
the bones and repair soft tissues to fix the
mechanical problem. That's the pathway. And finally,
while surgery is good for symptoms and function
now and can prevent further immediate damage,
its ability to completely stop arthritis developing
decades later is still being studied. It's about
long -term joint preservation. Well summarized.
If you found this deep dive helpful, we'd really
appreciate it if you could take a second to rate
the show or share it with someone who might find
it useful, maybe someone you know dealing with
persistent hip issues. And a final thought to
leave you with. Just consider how these seemingly
small variations in our anatomy, things we might
not even know we have, can have such a huge impact
on our movement, our quality of life, and our
long -term joint health. It really highlights
the importance of listening to our bodies and
seeking answers when things don't feel right.