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For more information, please see full course syllabus of Anatomy & Physiology
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Lecture Comments (7)

0 answers

Post by Justin Huang on August 10, 2017

My knee joint is also "double-jointed" so i can move it backwards.

3 answers

Last reply by: Bryan Cardella
Tue Nov 21, 2017 7:21 AM

Post by Justin Huang on July 16, 2017

I am double-jointed, but when I feel my arm, there seems to be a split and a second joint. The joint area is also significantly wider than others that are my age. Can you explain this scenario?

1 answer

Last reply by: Bryan Cardella
Mon Mar 14, 2016 1:46 PM

Post by Prajwal Jagadish on March 14, 2016

How does a person become "double jointed", being able to push bend an arm over 180 degrees, and what is actually going on.

Articulations (Joints)

  • Articulations, or joints, are either a synarthrosis (immovable), amphiarthrosis (slightly moveable), or synovial (free-moving)
  • The immovable joints include sutures, gomphoses, synchondroses, and synostoses
  • The slightly moveable joints includes syndesmoses and symphyses
  • The free-moving joints (synovial joints) typically contain articular cartilage, a joint capsule, synovial membrane, bursa, spongy and compact bone, and the periosteum
  • Synovial joint movements include flexion, extension, abduction, adduction, supination, and pronation
  • Synovial joints can be classified by type according to movement via the terms hinge, pivot, gliding, ellipsoid, saddle, and ball & socket
  • The knee joint is the most complex in the human body and it includes numerous ligaments and menici in the joint capsule
  • Joint conditions/disorders include arthritis, bursitis, bunions, dislocations, and hyperextensions
  • Did you know…
    • Q: What actually happens when you crack your knuckles? (or other joints?)
    • A: Cracking a joint usually involves the squeezing out of gas from the joint capsule (bursa). The reason why some people can’t continuously crack the same knuckle over and over is that it takes some time for the gas to build up again before being able to make that noise. Also, it is possible that a cracking sound could be generated by a ligament or tendon snapping back into place (some people can make this noise over and over repeatedly.)
    • Q: What makes someone double-jointed?
    • A: “Double-jointed” is a misnomer (not an accurate term based on what it literally means). At the site where someone can bend past the normal distance there is actually just one joint. They simply have abnormally flexible ligaments connecting the bones to each other. There have to be some genetic factors associated with this elasticity because practicing it over time does not mean that your joints will get to be “double jointed”.

Articulations (Joints)

Lecture Slides are screen-captured images of important points in the lecture. Students can download and print out these lecture slide images to do practice problems as well as take notes while watching the lecture.

  • Intro 0:00
  • Types of Joints 0:06
    • Synarthrosis
    • Amphiarthrosis
    • Synovial (Diarthrosis)
  • Kinds of Immovable Joints 1:09
    • Sutures
    • Gomphosis
    • Synchondrosis
    • Synostosis
  • Types of Amphiarthroses 5:31
    • Syndesmosis
    • Symphysis
  • Synovial Joint Anatomy 6:49
    • Articular Cartilage
    • Joint Capsule
    • Synovial Membrane
    • Bursae
    • Spongy / Compact Bone
    • Periosteum
  • Synovial Joint Movements 10:34
    • Flexion / Extension
    • Abduction / Adduction
    • Supination / Pronation
    • Depression / Elevation
    • Retraction / Protraction
    • Circumduction
  • Synovial Joint Types (By Movement) 13:56
    • Hinge
    • Pivot
    • Gliding
    • Ellipsoid
    • Saddle
    • Ball & Socket
  • Knee Joint 17:49
    • Typical Synovial Joint Parts
    • Menisci
    • ACL Anterior Cruciate
    • PCL Posterior Cruciate
    • Patellar Ligament
  • Joint Disorders / Conditions 21:45
    • Arthritis
    • Bunions
    • Bursitis
    • Dislocations
    • Hyperextension

Transcription: Articulations (Joints)

Hi and welcome to www.educator.com.0000

This is the lessons on articulation, also known as joints.0002

We are going go to call joints either of these 3 terms, based on how they move or do not move.0005

The first one is synarthrosis would be those joints that are completely immovable.0015

Sometimes when you are in the uterus as a developing baby, you might have slight movement because there are still forming0022

and there is still a little bit flexibility but by the time you are born and they are fused, sometime it takes you to early adulthood by the time they are completely fused.0029

Synarthrosis are completely immovable joint.0039

An amphiarthrosis is the middle ground that is one of those joints that are slightly movable in certain circumstances but not as movable as something like this.0042

Finally is the diarthrosis or the synovial joints those are the ones that are freely movable.0053

There is a wide variety of movements depending on what particular joint you are talking about in the body.0061

We will get to those later.0066

We are going to start off with those synarthrosis, the completely immovable joints.0067

The first one is sutures and this is most obvious in the skull.0074

Here is an image of a baby’s head and if you could see through the baby’s skin you can see that the surface of their skull has sutures0079

connecting all those different cranial bones.0089

As we mention before in the skeletal system lessons, you got fontanelles and the most prominent one is the anterior fontanelle.0095

There is another little fontanelle here.0102

Those are the soft spots and one day those are going to be completely gone because those bones of the cranial section of the skull are meant to be completely fused.0104

You have those fontanelles for a couple of different reasons.0115

That the baby can have a little room when it is coming out of the birth canal0118

and also to accommodate that massive amount of brain growth that happens in the first couple years of life.0122

Sutures not just in the skull but they are found all through out the body.0128

A classic example of a gomphosis would be found here.0133

The way that all your teeth connect to the mandible and maxillae, that connection that s not supposed to be movable is known as a gomphosis.0145

Of course you are going to loose your baby teeth but once the adult teeth is coming you are not supposed to move those.0155

If you have a movable adult tooth, you have a problem.0160

Synchondrosis there is a couple of different examples that is another completely immovable joint.0164

If you look at how rib pair 1 connects to the maneubrium just posterior to the clavicles that is immovable.0170

The rib that is more inferior as you inhale and exhale, those costal cartilage is helping to adjust that but up at the top here0180

the way that rib pair 1 connects to the top of the sternum it is not supposed to be movable.0190

If you look at the epiphysial plate for instance here is a leg bone.0197

Here is a drawing of the tibia this section would be called the diaphysis and this section here and here is the epiphysis.0208

The way that I keep it straight is I imagine a circle here and I think of the shaft of the tibia or femur that is kind of the diameter of the circle0231

and epi means above or outside.0246

The epiphyses are outside of the circle.0249

The epiphysial plates you will find this band of soft bones or cartilage as the bone develops, as it grows and hardens,0257

the epiphysial plates will eventually get to their maximum distance from each other.0268

Epiphysial plates up here and down here.0275

Once the bone is fully grown, it stopped.0278

You can think of that finalize epiphysial plate that is no longer moving0282

As being another example of a connection between one part of the bone the epiphysis and the part the dipaphysis that is not supposed to be moving anymore.0289

A synostosis is when you have this bone and this bone, the 2 sides of the frontal bone fusing into an adult.0297

You would no longer see that suture.0311

It is not obvious when you look at the frontal bone, that suture is gone.0313

This fuses very early on and you can call it synostosis.0318

The other sutures that are more visible in an adult is slightly different.0323

These are the slightly movable joints the amphiarthrosis.0328

A syndesmosis is pictured here.0336

Down on the distal end of how the tibia and fibula connect, these ligaments here provide the syndesmosis.0340

Depending on how you move your feet and the lower parts of your legs there might be some slight movement but not very much.0353

Not as much as you have in this section of this body.0362

A symphisis would be when we look at those cartilaginous pads that are between the vertebrae.0366

Let us say here would be t1 and here would be t2, the top 2 vertebrae of the thoracic curvature, this cartilaginous pad0375

and how it connects to those bones are symphisis.0388

There is slight movement.0391

It is ever so slight movement with each individual pad in articulating bone that lead to huge movement0393

so you can see when somebody move their back around.0399

Those are amphiarthrosis, slight movement accommodated there.0403

The one we are going to spend more time on and the most interesting are the synovial joints.0408

The ones that are freely movable and more obvious to us.0414

Here are some of the classic parts you would see in a connection between 2 bones at these kinds of joints.0417

Articular cartilage, these are called articulations it is when bones are moving with respect to one another with this connection.0424

Cartilage in that connection it is important.0431

This blue here, this is the articular cartilage and if you jump of a high elevation those bones could slightly touch each together.0436

If it was not for that cushioning there you could have some more long term damage over time.0451

Having that cartilage as a cushioning and as a protection is very important.0455

The average synovial joint has that cartilage on the exterior of the bones that are connected at the joints.0462

The joint capsule tends to be ligaments.0469

Ligaments are that connective tissue fiber that connects bone to bone.0475

We can see on the outside of this you got these fibers connecting the bone to the top, the superior bone to the inferior bones.0479

This is a cross section like we are looking inside of a joint.0492

Often times you are going to have this joint capsule continuing on the anterior and posterior portion like in the knee, which we are going to look at up close.0496

There is a lot in that joint capsule.0504

The synovial membrane is what you see here in red.0507

The synovial membrane right here is the membrane that is lining this anterior joint capsule adjacent to the articular cartilage.0511

The next term is bursae.0527

A bursa is a fluid filled joint capsule that is lined by the synovial membrane.0529

It is important for many reasons, like lubrication that helps with moving the joint.0537

Distribution of nutrients is also important.0543

Those are classically found in synovial joints.0546

You have multiple bursae in the knee.0550

You got bursae here.0553

You got bursae all over the place.0555

One of the disorders that could happen associated with this is bursitis.0557

We will cover that a little bit in the lesson.0564

Spongy compact bone you are going to see mostly spongy bone because as we said earlier in the bones lessons0567

it is common especially in long bones to have that spongy bone at the epiphysis.0578

You have slightly of that compact bone if you go further down.0586

Further down you would see the end of that spongy bone and here is the medullary cavity and this part here and here you would see more compact bone.0590

This joint capsule can continue on further down here0605

The perisosteum is a little way from this drawing but that is the most superficial part especially in the diaphysis.0610

Right here you would see the periosteum.0624

Those were the main parts of the synovial joint.0628

When it comes to different kinds of movements there are opposite movements.0633

The most classic one is flexion and extension.0640

Whether it is the lower part of the leg, that kicking motion extending and flexing it is also here, same basic idea.0643

This would be flexion and this is extension.0651

When it comes to abduction and adduction it is a little bit different.0654

Abduction and adduction they are machines at the gym that corresponds to these terms.0661

The way I remember it is with the arms and legs or you can also talk about the fingers doing it.0666

Abduction is this I am doing and abducting when I am lifting.0673

This adducting, I think this is adding my arms together.0677

I have added them together so this is adduction when I go like this.0684

It is the same with the legs, there is a machine at the gym where you will put your legs0689

and you do the exercise where you are lifting the weight to bring your legs together that is adduction machine.0698

If you are doing where you are pulling your legs away that is abduction.0705

You can also say that you are abducting your fingers.0712

Supnation and pronation, this corresponds mostly to the hands and feet.0716

If I will go like this I am pronating and this is supinating.0723

Picture that my hands are my feet.0730

My feet used to pronate when I was very young.0735

Let us say your feet are supposed to sit like this when you are walking in your shoes.0737

My feet was inwards when I would walk and part of it was I was flat feet.0744

I do not have substantial arch on my foot and that contributed to it.0750

My mom noticed that something was up because on the soles of my shoes the more medial inner part would be worn away than the lateral part of the sole.0753

She asked the doctor what is the reason this is happening0765

She said your son pronates.0769

I have to train my self to slightly do supination a little bit more and walk a little bit more on the outside of my feet.0771

Now I walk like I am supposed to and I do not have that problem anymore.0779

Somebody who is doing this their feet is pronating and someone doing this is supinating.0783

Depression and elevation is something with your shoulders.0789

Retraction and protraction that is something as simple as this.0800

Circumduction you can do it with the leg and the arm.0805

This does not have an opposite because it is just 2 different directions of circumduction.0818

Those were the basic synovial joint movements there are slightly more you can get specific but these are the main ones.0827

We are going to look at synovial joint types according to what kinds of those movements they do.0835

Hinge joints tend to be in that flexion and extension group.0844

A hinge joint there is slightly movement that you could do but I hear people call this the hinge joint the way that this happens is like a hinge on a door.0849

You can close and open the door with each of these joints.0865

If you are doing this, it is written down here, the movement that is permitted to your fingers is the flexion and extension.0870

You could say that the jaw is a hinge joint.0882

Pivot joints a classic one would be the neck.0886

It is usually rotating back and forth a little but different that the flexion and extension.0896

Here is a pivot joint, the way that I am pivoting my atlas and axis, those are c1 and c2 at the top of the vertebral column.0904

Gliding joints I could say this would be a way that part of my pectoral girdle works.0915

The way that the clavicle glides a little bit at the surface of the maneubrium and sternum.0927

It is different than the ones that we went over so far.0935

Think of gliding as this kind of action.0939

This would be the surface of the sternum or the maneubrium and there is slight gliding0944

that is accommodated when this bone is moving in respect to the other.0950

Ellipsoid joint is like how the wrist bone moves with respect to the forearm bones.0955

It is a little bit different than gliding.0968

Think of it as being a little well and moving like this with respect to the well.0973

That would be an ellipsoid joint.0982

The way that these wrist bones or carpals move with respect to the forearm bones.0983

A saddle joint, you can think of the thumb is a little bit different than what is going on here.0989

The way that this particular metacarpal 1 fits with the radius here, that is a saddle joint.0994

It is slightly different than ellipsoid because think of the shape of the saddle it is different than a simple well.1007

A saddle has that classic look and you got something at the saddle.1013

Think of this bone sitting in here that is the saddle and my thumb is the little cowboy in the saddle.1019

Here is a saddle joint the way that these 2 come together.1028

Finally the ball and socket, that is one of the classic ones you will here about.1033

Ball and socket up here, the way that the head of the humerus fits into the rotator cuff.1036

You have a ball and a socket.1042

The other one down here at the hip your femur has a head on it and it fits into this bony well of the coccyx called the acetabulum.1045

That allows something like circumduction, a very smooth and circular motion in many different directions.1058

That is your ball and socket.1066

The knee joint is the most complex joint in the human body, there is a lot going on here.1069

I am not going to cover every single part but we are going to cover the main ones.1076

You got all the typical synovial joint parts.1082

You got your synovial membrane, bursae, joint capsule.1085

We are seeing only parts of the joint capsule here because a lot of the exterior stuff has been removed.1091

This is one of the classic pictures from Gray’s Anatomy. We have a posterior view of the left knee because I know that because the fibula is more lateral.1096

We are looking at the back of the left knee.1107

The first one is the meniscus and this is plural, menisci.1111

One of the definition of the meniscus is you look at a graduated cylinder, and you try to measure the water level on it.1116

You may have that from a basic science class that the water climb at the sides of the container and that can fool you in terms of how much water is there.1125

You are supposed to look at the bottom of the meniscus to see what the actual measure in ml.1134

The shape that water line has is similar to the meniscus.1141

If you were to take the tibia out of these and look down on the top of the tibia in a superior view, you will see a lateral meniscus here1146

and you would see the medial meniscus here.1156

It is a cushiony, cartilaginous pad that helps give some shock absorption to the knee.1160

Those are the menisci.1186

The ACL you will here about that, the Anterior Cruciate Ligament.1189

Anterior means towards the front, cruciate means crossing and1194

the reason why they have that term because the ACL and PCL, one goes like this and one goes like this.1203

It is like they are crossing over one another and from this view you could see the ACL that is this particular ligament1211

and it connects to the back side of the femur and comes down in the front and connects to the top front of the tibia.1220

That is why it is anterior because it is like it is coming out that way.1229

The PCL connects at the back of the tibia and comes up top to connect to the femur.1233

Those do cross each other.1245

There is also the TCL, FCL, there is a lot of ligaments in here.1247

Another one I want to mention is when you look at the front of this knee joint, the patella is shaped like this1255

and connecting the patella to the front of the tibia you got the patellar ligament.1263

There is another bursa in front of the patella.1273

It is a very tiny little fluid sac.1277

On top of the patella you have the tendon.1280

Tendons are different from ligaments in the fact that they connect muscle to bone.1285

Ligament is bone to bone.1289

This particular tendon connecting the patella connects to the quadriceps.1291

It connects to these muscles that are right in front of the femur.1297

Joint disorders and conditions.1301

A classic one is arthritis.1307

You here about arthritis a lot, it affects millions of Americans.1309

Osteoarthritis usually happens the older you get the more severe it gets in general.1312

Osteoarthritis is that wear and tear, doing a lot over many years, a lot of physical activity, hard work, manual labor, those things can contribute to osteoarthritis.1319

There are genetic factors that can impact those things.1333

Osteoarthritis happens over time.1336

There are medications that can help with that in terms of dealing with the pain.1342

There are certain injections that can add a little bit of that cartilage back to the scenario.1347

Dietary stuff is very important, getting calcium and vitamin D in your diet.1356

Having a healthy diet over the long run is going to minimize the chances of getting osteoarthritis.1362

That is more from wear and tear generally.1368

Rheumatoid arthritis is different cause.1371

It affects about .5% to 1% of the American population.1375

That is usually from your immune system attacking your joints.1382

We are not sure what are all the causes of that but it is a terrible disease and there is no cure for it.1387

There are medications that help deal with it, make sure that it is not happening rapidly but it is called an auto immune disorder.1394

That is not as common as osteoarthritis.1403

Bunion that is the most classic version of bursitis.1406

A bunion tends to happen at that connection between the metatarsal of the big toe and that first phalynx.1411

It looks like when you look at the big toe, you have a big projection coming out.1424

One of the ways it is going to happen is wearing confining shoes like high heels over many years,1442

that is one way of you could stress out the joint which leads to inflammation and swelling.1449

It can be something that gets very hard and painful.1454

There are surgeries that can remove the bunion but wearing comfortable shoes is going to help minimize the chances of getting a bunion over time.1460

Bursitis anytime you have irritation of the bursae in the joint cavity you can get bursitis.1472

It is not always just irritation from physical activity that is a very common way that you can get it but it also can be from an infection.1481

If you get a bacteria or virus inside the bursae and affects what is going on in there.1489

That can lead to that painful irritation in the joint.1494

There are lots of nicknames for different kinds of bursitis.1499

I have heard tennis elbow or student’s elbow.1501

If you are sitting at your computer watching this presentation like this and you do that a lot,1506

you could be a putting too much strain on the bursae inside of that elbow joint.1512

That could lead to bursitis.1518

The first dislocation that came to my mind when I thought of this is shoulder dislocations.1520

If that head of the humerus comes out of the rotator cuff and how it is supposed to fit very nicely, that is going to be painful.1532

That is going to minimize that movement that you can do with it.1540

Sometimes they can be easily popped back into place.1544

Usually if you have a dislocation once, it is more likely you can get one again in the future.1546

Sometimes surgery is needed to properly put a bone back where it is supposed to be in its articulation.1554

Last is hyperextension.1560

Hyperextension if you think about extending this particular joint or your lower leg, it has a maximum that it is supposed to go to.1563

I am at about 180 degrees and if I go to about 190 or 200, I can damage the joint.1572

Hyperextension sometimes they heal on their own with some rest and not using that particular joint.1581

Sometimes surgery is required to properly fix a hyperextension.1591

Thank you for watching www.educator.com.1595