All language subtitles for - Transcript #9

Hello, everyone, and welcome to our module on the knee.

The knee is a joint between the upper and lower leg, and the major structures in the knee are listed on the slide.

It consists of four bones.

The first is the femur.

This is the upper leg bone.

And then there are two lower leg bones, the tibia and the fibula.

And then finally, the patella is a bone that sits in front of the knee.

It's often called the knee cap.

There are four ligaments.

Two of them are crocheted ligaments, the anterior and posterior crochet ligaments.

And then there are two collateral ligaments, the medial and lateral collateral.

And then finally, there are two meniscus, which are structures that serve as cushions.

There's a meniscus shown here in this drawing.

There's the medial and lateral meniscus.

So in the next few slides, we'll go through all these structures and talk about exactly what they do in the knee joint.

And then we'll finish the video by talking about the problems that occur when one of these structures breaks down.

The femur, as I said before, is the upper leg bone shown in red.

And the drawing on the right side of the screen.

And what you need to be aware of is that where the femur meets the knee joint here, there are two bumps called condios.

One is medial, it's called the medial condyle, the other one is lateral.

It's called the lateral Condio.

And those will be important when we talk about the attachments of some of the ligaments in the knee.

Other bones of the knee joint are shown on this slide.

There are two bones in the lower leg.

The tibia is the larger bone, the fibula is the smaller bone.

And just like the femur, the tibia has a couple of bumps called condyles.

There is a medial condyle and a lateral condyle.

A number of muscles insert here.

There's also a little bump on the front of the tibia called the tibial tuberosity.

This is where a ligament that attaches to the patella inserts.

And then finally, the patella, or kneecap bone, is shown in the bottom right side of the screen.

Now, let's talk about the cruciate ligaments.

The word cruciate means cross shaped.

And there are two cruciate ligaments, the interior cruciate ligament or ACL, and the posterior cruciate ligament, or PCL.

And the reason they're called cruciate is because they cross each other and form an X.

They're both found in the middle of the knee joint.

You can see them in this drawing on the screen here.

The ACL is here and the PCL is in the back, and they cross each other and form an X.

The anterior cruciate ligament gets its name because it runs from the lateral femoral condyle shown here in this picture to the anterior tibia.

That's why it's called the anterior cruciate ligament.

And the job of this ligament in the knee joint is to resist anterior movement of the tibia.

If you try to pull the tibia forward in the lower leg, that movement is resisted by the anterior crochet ligament.

The posterior crucigate ligament runs from the medial condyle of the femur to the posterior tibia.

That's why it's called the posterior ligament.

And the job of this ligament is to resist posterior movement of the tibia.

If you try to push the tibia backwards against the knee joint, that movement is resisted by the PCL.

They like to show you MRIs of the knee on your Step one board exams.

And you don't need to be an expert radiologist.

You just need to be able to find some basic structures.

So let's talk about that.

Now, the first thing I recommend you do when you see an MRI of the knee is to Orient yourself by finding the patella.

The patella is easy to identify.

It's right here in the image on the left.

It's here in the image on the right.

And the patella is always the anterior portion of the knee.

The bone that's towards the top is going to be the femur.

And the large bone towards the bottom is going to be the tibia.

In the image on the left, you can see this black structure running and attaching to the anterior tibia.

Therefore, that must be the anterior crochet ligament.

In the image on the right, we've got another black structure attaching to the posterior tibia.

So that must be the PCL.

And here's another MRI where the two ligaments are shown in the same image.

Once again, you can Orient yourself by finding the patella.

The upper bone is the femur, the lower one is the tibia.

And you can see the ligament that attaches to the anterior portion is the ACL, and the one that attaches to the posterior portion is the PCL.

Now let's talk about the collateral ligaments.

These are bands that run down the lateral and medial side of the knee.

If you look at this picture on the bottom left side of the screen here, this is the patella that's the front of the knee.

And we've got the medial collateral ligament, or MCL, on the medial side.

And we've got the lateral collateral ligament, or LCL, on the lateral side.

If you look at the right picture, the knee is turned differently so that you can more easily see the lateral collateral ligament over here.

And the medial collateral ligament is more hidden.

So both of these run down the side of the knee, and their job is to resist Vegas and various deformities of the knee.

So let's talk about what these two words mean.

Now, a vagus deformity of the joint means that the distal bone in a joint moves away from midline.

So in the case of the knee, a vagus deformity means that the patient will become knock knee and the lower leg will be abducted or moved away from midline.

Shown on the screen is a drawing of a valuable deformity.

And you can see that this person's knee is pushed towards the middle so that the person is knock knee.

The lower leg is pushed away from the midline or out.

That means the lower leg is abducted.

And the way I've always remembered what a Valgus deformity looks like is, just remember that the V and Valgus is for an upside down V that the patient's lower legs form.

That's always worked for me.

A Veris deformity is the opposite.

In this case, the lower leg is pushed towards the midline.

This means that the patient will become bow legged with the knee pushed out and the lower leg will be a deducted or pushed towards midline.

So the job of the collateral ligaments is to resist these types of deformities of the lower leg and the knee.

So the medial collateral ligament attaches from the medial epicondyle of the femur to the medial condyle of the tibia.

If we go back to this picture of the femur, the lower part of the femur that forms the knee joint has two large bumps called the lateral Condio and the medial condyle.

As I told you before.

In addition, there are two smaller bumps on the outside of the knee.

One is right here.

The other is right here.

They are called epicondyles.

There's a lateral epicondyle and a medial epicondyle.

And these are important as insertion sites for the collateral ligaments.

So the MCL runs from the medial epicondyle of the femur to the medial condyle of the tibia.

And its job is to resist Valgus or NOC knee stress.

And this should make sense to you.

It's on the medial side, so it's going to resist the knee from coming towards the middle and forming a knock knee situation for a person with their two legs.

The lateral collateral ligament runs from the lateral epicondyle of the femur to the head of the fibula.

If you look at this drawing on the screen here, the lateral collateral ligament is shown here.

It attaches to a portion of the femur called the lateral epicondyle.

The other end of the ligament attaches to the fibula.

So the smaller of the two lower leg bones, not the tibia, like the medial collateral ligament.

And the job of the lateral collateral ligament is to resist outward stress away from the mid line of the body.

This is called a various stress.

It's the type of stress that tends to make the legs appear bowed out or bow legged.

The last important structure in the knee joint we need to discuss are the two meniscus.

These are two Crescent shaped pads found in the medial and lateral portions of the knee joint.

They're made up of fibrous tissue and cartilage, and they sit between the tibia and the femoral condyles.

If you look at this drawing on the bottom right side of the screen, this is a meniscus shown here.

You can see that it sits between the tibia at the bottom and the femur at the top.

In MRI images, the meniscus usually look black.

So this is one of them here, and this is the other one right here.

It's this triangular shape thing here on either side of the knee joint.

So if you understand the slides I just went through on knee anatomy and the function of the structures, then it's very easy to understand.

Knee injuries.

Knee injuries often involve tears of either the ligaments or the meniscus.

They usually present with swelling and a feeling of instability in the knee.

Patients often complain of a sensation that their knee will give out.

Shown on the screen is an example of a knee injury.

You can see that the right knee of this patient is swollen and injured.

Let's start by talking about an ACL injury of the knee.

This is the most commonly injured knee ligament, and this usually occurs due to a non contact athletic injury.

It's often a person who is running or jumping and makes a sudden change of direction, like cutting or pivoting.

If you watch a lot of NFL football, this is a classic injury to occur in a running back who makes a sudden change in direction to try and avoid a tackle.

This is usually not caused by someone having trauma to their knee, like being tackled on their knee joint.

And classically, the patient reports a sense of a pop in the knee.

So when this injury occurs, the knee will be swollen and unstable.

And the way you can make the diagnosis of this at the bedside is to put the patient in a subpoen position lying in their back and test for the anterior draw sign.

The way you do this is you bend the knee at a 90 deg angle and you pull the tibia forward.

And remember what I told you before.

The ACL resists forward movement of the tibia.

If you see exaggerated forward movement greater than normal, that suggests an ACL tear.

There's also another test called the Lockman test.

It's the same as the drawer sign, but you use a 30 degree angle.

But the point here and what you want to remember for your boards is that the job of the ACL is to resist anterior forward movement of the tibia.

And that's what will be abnormal if the ACL is torn posterior.

Cruciate ligament injuries, in contrast, often occur from trauma.

They typically happen when there's a force directed posteriorly at the knee.

The classic cause is a Socalled dashboard injury.

It's a car crash where the person's knee goes into the dashboard and pushes the lower leg backwards and tears the PCL.

And you can diagnose the PCL at the bedside by testing for the posterior draw signs, very similar to the anterior draw sign.

You put the patient's supply on their back.

You bend the knee at 90 degree and you push the tibia backwards.

If it moves backwards more than normal, that suggests a PCL tear because remember, the job of the PCL is to resist posterior movement of the lower leg.

The MCL is often injured by a vagus stress.

Remember, it's found on the medial side of the knee.

So a stress that pushes the knee mediator pulls the lower leg laterally can stress that ligament and can potentially tear it.

This could be a contact injury.

Like if someone is tackled in a football game from the side of their knee.

It can also be a non contact injury if the person twists their lower leg and knee.

On physical exam, what you see in an McLaren or injury is abnormal passive abduction of the knee.

So to do passive abduction, what you do is apply a force to the lateral side of the knee.

That's a vagus stress.

So you push the knee inward.

And then you bring the lower leg outward.

That's abduction.

That's why it's called passive abduction.

So you're passively moving the lower leg away from midline.

The knee is being pushed towards the midline.

And if there's an MCL tear, the medial space will widen.

Remember, the MCL runs down the medial space.

So if it's torn, that space will widen when you perform this passive abduction maneuver.

The unhappy triad is a triad of knee injuries that are common in context sports.

They occur when lateral force is applied to the knee.

When the foot is planted.

Basically, if the person has their foot planted.

And someone whacks them from the side and pushes the knee towards the midline.

That's what causes the unhappy triad.

It was originally described as three knee injuries.

An ACL tear and McLare sprain.

And a medial meniscus tear.

There are more modern studies that now suggest that it's actually the lateral meniscus.

That is more commonly injured in the unhappy triad and not the medial meniscus.

There's a reference at the bottom of the screen if you want to read more about this.

And here's a picture to show you how this happens.

So this is the outside of the knee, the lateral side of the body.

A force comes in this way.

You can just imagine a football player tackling a person.

It pushes the knee towards midline.

What that's going to do is tear the ACL tear, the MCL.

And it will also tear the medial meniscus.

Although, as I said before, the lateral meniscus is also often injured.

It's hard to injure your lateral collateral ligament in isolation.

That's because it's on the outside of the knee, as shown here in this drawing.

So you need a force on the inside of the knee.

And this is very uncommon in sporting events.

It's very unusual for someone to get between the legs of a player and push outwards.

So therefore, you rarely see an LCL injury in isolation.

It often occurs with massive trauma to the knee.

That just damages lots of ligaments, including the LCL.

The physical exam finding with an LCL injury is abnormal passive, a deduction.

So this is the opposite of what we talked about for an MCL injury.

To test passive aduction, what you do is apply a force to the medial side or the inside of the knee.

That's a various force, and the lower leg is pulled towards midline.

That's a deduction.

And when you do this, you will stretch the lateral space of the knee and it will widen more than usual.

If the LCL has been torn, the medial or lateral meniscai can be torn.

This often happens when the foot is planted and there's a sudden change in direction and a twisting of the knee.

It often happens in sports like soccer or basketball.

The patient presents with pain and swallowing following their injury, just like most knee injuries, although the pain may be worse with twisting or pivoting, which are motions that put special stress on the meniski.

The bedside test for a meniscal tear is called the McMurray test.

To do this test, you put the patient sepine.

For example, if this is the head and these are the arms you have, the patient lies to pine.

The patient then bends at the hip and flexes the knee.

The examiner puts one hand on the knee and one hand on the lower leg.

The examiner then extends the knee so that the leg becomes straight while rotating the foot.

And if there's a pain or pop, this is called a positive McMurray test.

If you do this when you are internally rotating the tibia, meaning you are twisting the foot toward the midline, this is testing the lateral meniscus.

If you do this when you are twisting the foot away from midline, that's called external rotation and you are testing the medial meniscus, I'll finish this video with a couple of knee injuries that don't involve the meniscus or the ligaments.

So first let me make a general point here.

The knee is an example of a synovial joint.

There are many synovial joints in the body.

These joints connect bones and have a synovial membrane, and they're filled with synovial fluid.

This is a drawing of what one would look like on the screen here.

This is the synovial membrane, and there is fluid in the joint space.

So synovial joints like the knee often are surrounded by Bursa, which are small sacs that also have a synovium.

And the role of the Bursa is to serve as a cushion between bones and tendons and muscles.

And there are four Bursa that are found near the knee.

And shown in this picture is a generic example of what a Bursa looks like.

So if you've got two bones here and they're surrounded by a synovium on the outside, you've got these little sacks called Bursa.

And they are sort of slippery and mobile sacks that cushion the space between tendons, ligaments and the bones.

So prepatellar bursitis is inflammation of the prepatellar Bursa.

As the name implies, this often happens when people repeatedly kneel.

It's sometimes called housemaid's knee because housemaids are often kneeling, and this causes damage and inflammation to the pre potential, or Bursa, and that leads to prepatellar bursitis.

There are, however, other causes Besides trauma, things like infection and gout.

It presents as pain with activity of the knee, swelling anterior to patella and warmth, very easy to diagnose, usually treated just with insights.

Another knee condition is called a Baker's cyst or a Papyal cyst.

And it's called a Papyl cyst because it consists of a fluid collection in the papyl space at the back of the knee.

In a Baker's cyst, fluid collects in the Bursa between the gastricnemius and semimembernosis muscle tendons.

If you look at this picture on the right side of the screen here, the gastric nemius is in the lower leg.

The semimembiosis is in the upper leg.

They both have tendons that insert in the back of the knee.

And there is a Bursa found there called the gastrocnemius semimembrosis Bursa.

And if it fills with fluid, that's what causes a Baker's cyst.

And what you need to know about this condition is that this Bursa between these two muscle tendons often communicates with the synovial space of the knee.

So people who have chronic joint disease of the knee in any form of arthritis often have fluid accumulated in this Bursa.

So, for example, people with degenerative osteoarthritis or inflammatory arthritis or any type of joint injury will often go on to develop a Baker's cyst because the synovial space of the knee will communicate with the Bursa behind the two muscle tendons.

These cysts are often small, and asymptomatic they're sometimes felt on physical exam, they're also sometimes detected when the knee is image for an unrelated joint symptom.

They can cause posterior knee pain, which should make sense to you.

They're found in the back of the knee.

Sometimes the pain is worse with standing, sometimes it's worse with activity, and occasionally these cysts will rupture and cause acute pain in the lower leg that can mimic a deep vein thrombosis.

And if you just remember that these types of cysts often happen in people who have knee inflammation, and it's easy to remember that these are common in patients with rheumatoid arthritis, which often involves the knees.

Shown on the screen are two MRI images of very large Baker cyst.

You can see the white fluid collections in the back of the knee.

That is a Baker's cyst.

Osgood Schlatter disease, which is also called tibial tuberosity evolutions is a disorder that occurs in children where they develop pain and swelling at the tibial tubrical from overuse of the knee.

The tibial tubrical is a swelling in the tibia shown here in the picture where the patellar tendon inserts.

So from overuse, with the patellar tendon tugging on the tibia.

At this point, that can lead to pain and swelling.

And one of the key things you need to know about this portion of the tibia is that this is the secondary ossification center of the tibia.

This is a tie in with bone biology and bone development.

Our long bones ossify in utero they're initially cartilage but they ossify into bones at two centers.

One is called the primary center one is called the secondary center and the secondary center of ossification is what eventually becomes the tibial tubical which is what becomes painful and swollen.

In Oscar Slaughter disease this is usually a benign condition.

It's usually self limited.

It will be a child who presents with pain and swelling just below the kneecap.

I'll finish this video by discussing a patellar fracture.

This results from trauma to the knee.

It presents as a swollen painful knee and what you want to always remember about this for step one of your boards is that patients with a patellar fracture cannot extend their knee against gravity.

To understand why this is the case let's look at the drawing in the bottom right side of the screen.

The patella connects the quadriceps tendon above to the patella ligament below which attaches to the lower leg.

So when patients try to extend their lower leg or extend their knee the force from the quadriceps is transmitted through the patella bone.

So if there's a fracture the patient won't be able to extend their knee against gravity.

This indicates some reason for loss of knee extension.

The classic cause is a patella fracture although you can also see this if there's a tear in the quadriceps tendon and you can also see this if there's injury to the patellar tendon and it's usually diagnosed by X ray this is a picture of a patellar fracture on the top right side of the screen.

Here you can see that the patella bone which is on the left side of the image has a fracture down the middle and that concludes our video on the knee.