(intro music)
- Your anterior cruciate ligament, or ACL
is the most commonly injured ligament of the knee.
It's one of four stabilizing ligaments of your knee.
You ready for this?
There's the PCL, posterior cruciate ligament.
The MCL, the medial collateral ligament.
The LCL, the lateral collateral ligament,
in addition to this ACL, the anterior cruciate ligament.
Your ACL is located in the center of your knee,
and runs from the back of your femur, or thigh bone,
to the front of your tibia, or shin bone.
Your cruciate ligaments cross like an X,
that's why we call them cruciates,
and they're in the center of your knee.
These cruciates, the ACL and the PCL,
are responsible for limiting the front-back movement
as well as rotation of your knee.
Those collateral ligaments, the MCL and the LCL,
they limit side-to-side movement.
You depend on that ACL to walk, run,
but especially to jump, twist, and pivot.
ACL tears, anterior cruciate ligament tears,
can occur by themselves, we call these isolated tears.
But frequently they can occur with some other injuries,
such as injuries of the MCL or the LCL or the meniscus.
Let's look at the front view of the right knee.
First of all, the thigh bone, called the femur,
that sits on top of the leg bone, called the tibia.
We have the two meniscus, or shock absorbers,
between the bones.
then we have a series of ropes or ligaments
that connect the outsides of this knee.
The ligament on this side, or the outer side
is called the lateral collateral ligament, the LCL.
Then it's partner on the inner side here,
that again starts on this shelf,
but now attaches more broadly along this inner side
of the leg bone.
And this is called the MCL.
We have two ligaments that cross
in the middle of the knee.
These are called the cruciate ligaments,
because they cross.
We have, first, the anterior cruciate ligament
that runs in this direction,
the ACL.
Then, running behind it, it's partner,
the posterior cruciate, PCL.
Superimposed over the front,
we can draw the kneecap, or patella.
If we draw a side-view of this knee,
it looks something like this.
Here's the thigh bone, or the femur.
Here is the meniscus,
attached to the leg bone.
If we look in profile at the kneecap,
it looks something like this.
Then the kneecap is attached to the leg bone
by the patella tendon.
And then we have another tendon here,
the quadriceps tendon that attaches the thigh muscle,
called the quadriceps, that pulls in this direction.
If we looked at a cross-section through
the middle of this knee.
In other words, if this were the cross-section.
In the middle of the knee,
the anterior cruciate ligament attaches up here
on the thigh bone, and down here on the leg bone.
We have what is really a check reign
type of ligament, or rope.
This rope prevents this bone, the leg bone,
from translating forward, because it's hooked up
from here to here, so it prevents this motion.
What happens when you tear
your anterior cruciate ligament.
Most of the time, you tear it right through the middle,
here, which is right through the middle here.
And when that happens,
you now have the ability of this leg bone
to move forward and you have an unstable, or loose knee.
When that happens, it needs to be fixed.
ACL tears are most commonly caused
by sports-related injuries.
However, anyone who has one of these mechanisms
of injury can tear their ACL.
Some common causes or mechanisms include
a sudden de-celeration,
like when you stop or slow down quickly.
A hyper-extension of the knee,
or a sudden pivot or change of direction,
like you if step in a hole in your yard.
Studies show that women, however,
are two to four times more likely
to tear their ACL than men.
Why? Well, this is probably due to a number of factors.
First of all, women often have a strength imbalance
between the muscles in the front of their thigh,
their quadriceps, and the muscles
in the back of their thigh, the hamstrings.
More women than ever are competing in athletics,
and as such, the number of injuries has increased.
Poor body mechanics, however, during jumping,
landing, cutting, or pivoting,
can also attribute to the increased number
of ACLs in women.
Finally, ladies tend to have looser,
more flexible joints than men,
making them more prone to these ACL tears.
(outro music)