This is the most commonly sprained ligament in the human body — the
anterior talofibular ligament. You’ve probably sprained it yourself, and seen
the resulting pocket of swelling bubble up on the side of your foot, right under the laces.
Since they’re so common, we tend to write them off as benign injuries,
but collectively, they’re a big deal.
Ankle sprains alone make up 3-5% of emergency room visits a day in the UK, and 2 million ankle
sprains a year in the US. And a quarter of the people who sprain their ankles end up missing
work because of their injury. Then as they recover, they have to deal with the cost of
physical therapy, or any of the ankle stabilizing products out there from tape to sleeves to braces.
So what is it about our ankle anatomy that gets us to hurt
ourselves so frequently? And what, if anything, is the best solution?
Hello and welcome, if you’re new here,
my name is Patrick and this channel is all about anatomy and physiology.
There are three big bones we need to keep track of. The tibia and fibula in the lower leg,
and the talus of the foot. If we want to get super technical,
the scientific name for this joint is the talocrural joint — talo for the talus bone,
and crural just refers to the tibia and fibula together. The talocrural joint is a hinge joint,
which means it can move in two directions: it can dorsiflex thanks to the muscles
like the tibialis anterior, and it can plantarflex thanks to the calf muscles.
But what we colloquially call the ankle is two distinct joints. There’s the talocrural joint,
but there’s also the subtalar joint — or the joint between the talus and the calcaneus, or heel bone.
This is the joint that lets our ankles move side to side, or invert by going in,
and evert by going out. The foot, the tarsal joints, get involved when we invert and evert too,
but we’re going to focus on the subtalar joint for this video.
For eversion, the peroneals on the outside of your lower leg pop out nice and prominently, but the
muscles of inversion, like the tibialis posterior are deep and harder to see. Either way, you
can actively flex those muscles and see how you control inversion and eversion on your own body.
The big danger is going too far in one direction, which is what causes ankle sprains.
Luckily we’ve got a few pieces of anatomy that keep us from inverting or everting too far.
Like the lateral malleolus, that bump on the fibula, extends further down your foot than
the medial malleolus of the tibia. This is one of the reasons we can invert more than we can evert.
But before we even start hitting bone, our ligaments keep us from going too far
one way or another. On the medial side is the deltoid ligament, which is actually made of four
smaller ligaments. But even without it, we don’t tend to experience an
excessive amount of eversion though normal walking or even most sports.
So while eversion ankle sprains do happen, they’re pretty rare.
On the other side, are the three lateral ankle ligaments. There’s the calcaneofibular ligament
which connects the tip of the fibula to the calcaneus, then the posterior and anterior
talofibular ligaments but we’re focused on the anterior talofibular ligament, or ATFL.
All of these lateral ligaments are supposed to keep us from inverting our ankles too much.
But when they undergo too big of a mechanical load, like when you land sideways on your
foot after shooting a layup, you can stress those ligaments or potentially tear them, and that’s an
ankle sprain. Oftentimes, folks in sports medicine will just refer to these injuries collectively as
lateral ankle sprains to denote that a bunch of those ligaments were injured,
but the ATFL is the weakest of them and most frequently sprained.
But if these things are supposed to keep us from an excessive range of motion,
we need to dig a layer deeper. Why are our ankles exposed to excessive inversion in the first place?
The first answer lies in the talus.
On diagrams, the talus looks like a big square chunk, but in reality,
it’s wider anteriorly towards the toes, and narrower posteriorly towards the heel. So it
ends up forming this wedge that changes position depending on how dorsiflexed or plantarflexed the
joint is. When the ankle is dorsiflexed, the talus firmly wedges into the joint.
The bones are in maximum contact with each other, which makes the joint extra stable.
Kinesiologists call this the close packed position. But when you point your toe,
the talus unwedges itself and it can wiggle more freely. This is the open packed position
allowing it to wiggle more freely, it’s also way less stable. Feel free to take your shoe off and
feel this for yourself. You’ll notice much more motion when your toes are pointed.
And when we exercise or do sports, we are constantly in the open packed position.
When we jump and land in basketball, when we cut sideways on the soccer field, or when we dance.
Even outside of traditional sports, anytime you wear a high heel, your ankle is in
the open packed position. How people then dance in heels is beyond my comprehension.
And why that is a big deal: once we’re in an open packed position,
it’s a lot easier to get into excessive inversion.
But as multiple studies pointed out,
half of all ankle sprains happen outside of the sports or exercise setting,
so no matter your lifestyle, you’re still at risk. Some of that can be attributed to the
dangers of the outside world like curbs and uneven walkways but anatomy accounts for a lot of it.
But the second anatomical clue lies in our muscles. If we had no ankle muscles,
the foot would fall into the open packed position on its own thanks to just,
you know, gravity. But thanks to the gastrocnemius and soleus, which tend to be tight, the ankle
gets a little extra nudge into plantarflexion when the foot is off the ground.Which means,
you guessed it, open packed position and more excessive range of motion
The third clue is the simplest: our ankles deal with our entire body weight thousands of times a
day. Multiply the number of steps or landings over your athletic career, and you’ll have millions of
opportunities for the entirety of your body weight to come down on one little threadbare ligament.
So a quick recap. Our ankles have ligaments that should prevent them from going into
excessive range of motion. But thanks to the shape of the talus, a slightly
pointed toe predisposes us to excessive inversion and thus, lateral ankle sprains.
But here’s the extra insult to injury.
People who sprain their ankle once are more likely to sprain it again,
or to experience chronic ankle instability, which means you have symptoms for over a year after the
injury. Now, It’s hard to pin down exactly how common chronic instability is, but the high end
estimate is around 70% of people who sprain their ankles eventually develop it. It also
likely leads to arthritis and puts you at greater risk of falls as an older adult. So… not great!
So not only are we biomechanically predisposed to sprain our ankles,
but spraining it once sets us up for more sprains in the future. So naturally, people who work
in orthopedics are looking for ways to prevent first sprains and improve chronic instability.
One of those strategies is using an ankle brace, like a lace-up model that you’d
wear with your normal shoes, are a cheap and easy way to prevent first sprains.
A systematic review from 2010 looked at all the external ankle supports they could find like
braces and tape, and concluded that athletes who wore ankle braces
saw a 70% lower incidence of ankle sprains than athletes with bare ankles.
A differente 2010 review claimed that athletes who got their ankles taped
saw a 2 to 4 times reduction in first time ankle sprains compared to unsupported athletes.
But, as they pointed out, the studies they looked at weren’t the highest quality.
It’s hard to design a rigorous randomized controlled trial because you’d have to find
clinicians who could tape exactly the same way every time and follow
up the participants over a long period of time.
Another promising strategy involves injury-prevention training programs
that teach people landing mechanics and work on balance and strength — basically,
how to move without hurting yourself. But fair warning,
the research that studies these programs isn’t the most robust and suffers from small sample sizes.
The routines themselves are different, but you can generally expect exercises for balance and
proprioception. So a lot of single legged stability or hopping and agility exercises.
Hopefully hip stabilizing exercises too.
The downside though is the time. Most of these programs are 15 to 30 minutes each and done 2
to 4 times a week which means that they’re way more time-intensive than buying a brace.
But you also get the added benefit of greater balance, flexibility,
and other factors related to athletic performance. So it’s not just good for
preventing ankle sprains, it’s good for preventing athletic injuries as a whole.
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