Understanding Joints in Anatomy and Physiology

Hey everyone, welcome to Professor Long's Lectures in Anatomy and Physiology. I'm Professor Bob Long. If you're following along in these videos, you know that these videos are intended for use by students who are enrolled in my class at Del Mar College. I want you all to learn what's in my note set, what's in the textbook that we use, and what I write on the board. If you're not enrolled in my class, your instructor may cover more information on some subjects, less information, or even totally different subjects than I cover. Please learn the material that your instructor requires you to learn. Now, hopefully, my videos help you understand the more difficult subjects that you're going to be learning. material. So I'm trying to set a broad foundation where we can add details instead of just puking out all sorts of information. So if you find them helpful please hit like and or subscribe but definitely like the videos so that if I get enough feedback I know to continue to do them. Because we're in the pandemic these are done very quickly and crudely with my cell phone and me and a board. I hope to be able to make them a little bit sharper and nicer and more professionally done in the future. If I get enough likes, I'm going to invest in that endeavor. Anyway, we've been covering the skeletal system in Part 1 A&P. We've talked about the shapes of bones. function of bone, different types of ossification, bone growth and length and diameter. We've talked about fractures and fracture repair and the effects of nutrition and exercise and diet on our bone formation and hormones. So everything in our textbook that we use is in chapter seven. We're not skipping chapter eight and nine. That's what we're doing in lab, which is the different bones of the body and all the landmarks that you have to learn for the laboratory. So we're going to jump to chapter 9 now. We're going to start covering articulations. If you're following along in my notes, we're going to be on page 47 and 48. So, when it comes to an articulation, you should know the definition of the word articulation. Articulation simply means a joint. A point in the body where two or more bones come together and form some kind of joint, where they're joined together. Where they communicate. To articulate means to communicate, and to be articulate means that you communicate very well. So an articulation is a joint. communication between bones. Now most of the joints we think of are freely movable like your fingers and your wrist and your elbow and shoulder and other joints but there are some you may not be aware of and by the way before I get any further anytime you see the root word arthro anywhere in literature or in a report it's referring to the joint. When someone has arthritis it's inflammation itis of a joint. Arthrotic implants are implants into a joint. So anytime you see arthro, you're talking about joints. Now, when it comes to joints, joints can be classified in a number of ways. One way that we categorize or classify joints is based on their function. How much movement is in the joint. Another way that we can classify them is through how they are structured or put together, which is an extremely complex process. And I wish we had more time to go into it. For those of you that are going to do things like physical therapy assistant and occupational therapy assistant, or who are going for physical therapy and occupational therapy school or chiropractic school. We don't have a lot of time for that, so I'm going to try to set the fundamentals. But joints can be very difficult to classify. based on their structural assembly, okay? Because, you know, some of the joints are just extremely complex. But nonetheless, we're going to do our best, all right? So, if you're following along in the note set, at the top of the first page of this section, there's a little three-row and three-column table that asks you to classify joints based on their function. So when it comes to functional classifications of a joint, There's really only three major classifications, okay? One is called a synarthrosis. Syn means width, and arthro means joint. And if you're following along in the table, we consider these to be a bony fusion. Or actually, it's not really always a bony fusion. When we say synarthrosis, what we mean is little... or no movement in the joint. And it really is almost no movement. Okay? These are joints that are fused together. They can be fused with bone, or they can be fused with some cartilage or connective tissue, but there's not a lot of movement in them. That's why the two bones are with each other. A good example of this... When it comes to this column on the table where you get some examples, one of those would be the sutures of the skull. Your skull bones, especially the calvaria or cranium, they fuse together and there's no movement there. Or if you look at the os cocci, the three bones of the os cocci that fuse together, there's no movement there. So there's a couple of examples that I can ask, right? Which would be a good example of a synarthrosis or in a synarthrosis, how much movement is there? Okay, now I'm going to write the next one down, but I'm going to skip it for a moment and do the last one of the three. There's amphiarthrosis. Amphi means a little of both, like an amphibian from bio to live, and amphi both. They live both on land and in the water. And then there's a diarthrosis. So I'm going to do this one first for a reason. In a diarthrosis, these are said to be freely movable joints. It's two bones that are free or independent of each other that move together. And think of a diarthrosis as most of the joints in the body that we think of. So I'm not going to write them all down, but it would be fingers, wrist, elbow, shoulder, your hip, your knees, your ankles, your toes. Most of the joints that we think of, and a lot of the vertebral joints, intervertebral joints, not all of them, but most of them, are a diarthrosis where two bones are moving independent of each other. and antheroarthrosis is somewhere between the two and so these have some movement and i tend to think of these as those that kind of wiggle a little bit they're not freely independent but they can wiggle next to each other or move just a little bit. We have lots of examples of this you can list the knees and the elbows and shoulders and hips. For the amphiarthrosis this would include a few of these. One of my favorites is called the AC joint and AC stands for acromioclavicular joint. Now I'm going to abbreviate joint as a JT. You can name any joint in the body by taking either the more proximal or more medial bone, or the bone that does less movement, and the bone that does more movement. And so when we move our shoulder around... the clavicle is moving a whole lot and so we call this the acromioclavicular joint where the acromion process and the end of the clavicle come together. If I were to look down on top of this, I would see the spine of the scapula forms the acromion process and then the clavicle comes along here does this and there's a little band of connective tissue across there that lets those two things glide across each other okay so that's one good example another good example is what is called the tib fib joint which stands for tibiofibular joint okay Or I could have what's called the glenohumeral joint or the, you know, femoro-tibial joint. We can name any joint by naming the two bones or the two or more bones that form it. The tib-fib joint is the joint between the tibia and the fibula. So it's called the tibio-fibular joint or tib-fib joint. And if I were to look at these two bones, then if I have the proximal tibia and the distal tibia, along with the fibula next to it, There's a little bit of connective tissue here. And if you rotate on your knees without moving your feet, those two bones can kind of move a little bit, but they're not independent of each other. So they are usually bound by some kind of connective tissue that allows a little bit of wiggling. So it's almost as if someone tied your elbows and your hands together, you could still wiggle your arms a little bit. So those would be called an amphiarthrosis. So know these two examples for synarthrosis, these two examples for an amphiarthrosis, and know several examples for a diarthrosis. arthrosis. Now, each one of these categories, functional categories, can be broken up into several structural categories based on how the joint is put together and also how it kind of functions. So now, we're going to... to go into the structural classifications of joints and I'm not going to write all of this stuff on the board because a lot of it is filled in in my note set okay I'll fill in a little bit of the information with you but if you were following along in my note set for those of you enrolled in my class we've taken the three functional categories and broken them out on this table and then there's a whole bunch of the structural classifications within those functional categories So for example, synarthrosis has three examples. There's a fibrous connection, and there's a cartilaginous connection, and then there's a bony fusion. These are fused joints, and are they fused with connective tissue? Are they fused with bone or are they fused with cartilage? So if I go through them, one of the fibrous connections between bones would be called a gomphosis. Now I'm just going to be honest with you guys. I probably shouldn't say this for those of you enrolled in my class, but I don't really like the way that our textbook does this because several of the joints can fall under different categories depending upon the type of bone. How the joint is put together and also sometimes dependent upon the stage of development. For example, when our suture bones of our skull are growing together and they haven't interlocked and fused, there's some connective tissue, the fontanelles that hold them together. And so the sutural type joints can have some fibrous connective tissue between them and they have very little movement. When it comes to what's called a gomphosis, a gomphosis is the periodontal ligament. That's the ligament at the base of each tooth. This is one of the ones I think people should know. When you're looking at the jaw, if I could look down at an angle at the top of the jaw and rip the teeth out, then you would see these little air pockets and for example your front teeth would sit in there with their root like this. And when you slide the tooth into the bone, There's a little piece of connective tissue that holds the tooth to the bone tissue in here. And those ligaments that go around the tooth happen to be called a periodontal ligament. And there is a little bit of wiggle. I mean, if you grab your tooth and wiggle it, it'll move a little. Please don't do that. It will loosen those ligaments and cause your teeth to fall out earlier in life, which is why you should never open things with your teeth. There's two problems. One, you scratch up the enamel and chip that up and damage the tooth. The other is you can weaken the periodontal ligaments. But we call this a gonphosis. And it's the ligament between the teeth and the mandible or the maxilla. And it is a type of synarthrosis. It's a type of fibrous connective tissue that's called a gonphosis. So if I ask you what is a gonphosis, it's the periodontal ligament around your teeth. And it's a type of synarthrosis. one of the ones that's a cartilaginous connection is called a synchondrosis. And this is when you have cartilage between two bones. But usually in a synchondrosis, I'm going to write something out because I want you to pay attention to this and know it. But when we talk about a synchondrosis, that is usually hyaline cartilage. between two bones and they have almost no movement. Some examples of this would be the growth plate during development or between the sternum and ribs and those cartilages happen to be called costal cartilages. The term cuesta means rib, and so the costal cartilages where our bones, where our ribs join our sternum, allow a little bit of movement, but not much. And at the growth plates when our bones are developing, if I have the diaphragm... epiphysis and the epiphysis here, that growth plate is hyaline cartilage. And there should be very little to no movement there. We call that a synchondrosis. And one of the things is that they have hyaline cartilage connecting two bones. those two examples. Okay now if I follow along on the list the next one would be a bony fusion which is called a synostosis and if you look at the name it tells you chondrosis is cartilage, ostosis is a bony fusion. This is where bones are completely fused together and again good examples of this would be the sutures of the skull and the os cocci. These bones are completely fused together, especially as an adult our sutures have completely grown together. And so we call that a synostosis. It's a bony fusion. Now all of these are synarthroses, meaning no movement. The next... category we talked about was an amphiarthrosis and under amphiarthrosis there's a number of different types of subcategories and I'm going to talk about a few of them the ones I read on the board are the ones you should at least in my class you should really pay attention to so when it comes to an amphiarthrosis they can be bound with some fibrous connective tissue or with some cartilage and so One of the ones that's got some fibrous connective tissue in it is called a syndesmosis. A syndesmosis has collagen fibers or fibrous connective tissue, okay? There's usually a substantial ligament holding these two bones together. They almost always involve what we call would be a ligament. Now, some examples of that I've already given you. We talked about the AC joint, and we've talked about the tib-fib joint. Those would be examples of a syndesmosis, where there's a fibrous band of connective tissue holding the joints together. And the cartilaginous version of an amphiarthrosis would be called a symphysis. And there's one really good symphysis in the body. And one of the keys to this is that this has fibrocartilage holding the joint together. These are fibrocartilage. If it's hyaline cartilage, then we call that a synchondrosis. If it's a symphysis, it's fibrocartilage. And the best example is the pubic symphysis. Okay? Where the os coxi come together at the pubic bones. You would have the obturator foramen here, okay? There's some fibrocartilage holding this together that makes it a very strong but somewhat flexible joint, okay? So that would be the symphysis. The remainder of the... the types of joints I'm going to cover are all called diarthroses, freely movable joints. And there's a whole bunch of those. And these are probably the ones that most of y'all, especially if you go into any kinesthetic type of therapy like OTA. and PTA you're going to be dealing with some of these joints okay so I'm going to run through their categorizations and give examples and that's where the questions will come from on exams and state boards so you need to know this information so these are all also classified as synovial joints because they have a synovial membrane that surrounds them and are filled with synovial fluid which lubricates them and provides some shock absorption okay so the first one that's on our list is called a ball and socket joint. And when we talk about a ball and socket, what we're really talking about is a head and a cup. There's two really good examples of these. In our shoulder, we have what's called the glenohumeral joint. And I didn't write humeral out very well. It's glenohumeral joint, okay, from the humerus of the body. So the glenoid cavity, if you look at the scapula, it has the glenoid fossa and the head of the humerus. of your shoulder make what's called the glenohumeral joint. There's a whole fibrous capsule that surrounds that. So that's one example of a head in a cup. The other example would be your hip and that would be called the acetabulofemoral joint. Now this would be the scientific name the acetabulofemoral joint. So if you study the bones in lab you know that the femur has a head on it. We would have the greater and lesser trochanters. We've covered that anatomy in lab. And then you have the acetabulum of the os coxi where it fits. So it's a head in a cup. Those are two examples of what's called a ball and socket joint. Now, when we talk about joint movement, the joints can move in what we call an axis. If they move... in one axis or one direction only it's called a monoaxial joint. Mono meaning one. If they can move in two directions or two axes then it's called a diaxial joint. If they can move in three or more directions it's called a triaxial joint. Your shoulder is triaxial in the sense that it can move in a number of directions and a number of planes at all these different angles and it can move sort of in a cone shape. So these ball and socket joints usually have the most or the largest range of motion. Now the next one that's listed by the way is a pivot joint. Well if any of y'all ever played basketball you know what pivot means. If you stop dribbling and you pick up the ball you can only move one foot the other foot has to be planted on the floor so you can move in circles call that pivoting and so these have a rotational motion but they only rotate in one axis like spinning you know a good example of this would be c1 and c2 between the Atlas and the axis if you recall the axis of the vertebrae has this little ball sitting on top called the dens and the atlas wraps around that and it allows you to rotate your head or pivot so c12 or the adlo axis joint is a good example of a pivot joint another one is part of your elbow but what we call the radio humeral joint And some books call it the humeroradial joint and that's okay. Where the end of the humerus is, we have the lateral epicondyle, we have the capitulum, we have the trochlea, and then we have the medial epicondyle. Well the head of the radius fits right here and so the radius allows you to pronate or supinate or pivot your forearm. That would be a pivoted pivot type joint okay. Those are two good examples and you should know those. The next one on the list is a condyloid joint. Condyloid joints can go by a number of names and oftentimes people will often refer to these as well as a cam joint. I've heard it both ways in the field of orthopedics. But these involve condyles. Wherever you have a condyle on a bone, like the mandibular condyle or the femoral condyles, You have a condyloid joint, okay? You also have them where our fingers are. So, some good examples would be the, what we call the temporomandibular joint, also referred to as the TMJ for those of you who do dental hygiene. Between the temporal bone and the mandibular bone, there's a joint and there's some cartilage there. When you grind that cartilage off from grinding your teeth, or be called what's called a bruxer, when you grind your teeth at night, you're wearing that cartilage out and you get what's called TMJ disease or arthritis in the temporomandibular joint. Another good example would be our knee and it would be called the femorotibial joint. The condyles of the femur fit on the condyles of the plateau of the tibia. So we call that ephemero-tibial joint or their condyloid. And also between your phalanges, the what we call the IP joints. If you ever hear that term what it means is inter-phalangeal joints. Now if you take a good look or actually I should say it's the CMC joints. The carpo, oh no, I'm getting that wrong. Please forgive me. I'm trying to think of the right joint in the hand. It's the metacarpophalangeal joint. Sorry, I worked for a hand surgeon. I should know this, right? MP stands for metacarpophalangeal joints. So if you look at the ends of the metacarpals, they kind of do this. They have a condyle, and the phalanges sit on that like this. And as you flex your finger, if you keep your finger straight, but you bend them at the MP joint, the metacarpophalangeal joint, they can do this. Now one of the things about condyloid joints or cam joints, if you fracture a bone, You don't want to usually under 99% of the circumstances, you don't want to cast the joint straight. For example, if someone has a cast on their hand, you usually see the wrist like this and the fingers are bent like this instead of straight. When someone has a fractured leg and they cast the knee, they almost never completely cast the knee, at least for long periods of time, straight. It's always got a little bit of a bend in it. And the reason is this, the distance from this point where the... where the ligaments attach to here is shorter and the ligaments are a little more slack. If I flex my fingers this distance from here to here here is increased now. It might only be that long there, but when I increase it, it tightens those ligaments. And a quick experiment that you can do is if your finger is straight, you can wiggle your finger back and forth like this. But if I bend my finger a little bit, it becomes much more difficult to wiggle that joint. The joint becomes tighter because I've stretched that ligament that's holding it together. Now, if I casted it straight, While I cast it, a lot of times the connective tissue will also tighten up and then you can't flex your fingers. You lose range of motion. It's very difficult to get that back. So that's why people will cast certain joints at an angle and it's usually a cam joint or a condyloid joint. You want to be somewhere in the middle of these two so that you don't lose any range of motion. Range of motion of a joint is just as important as the strength of the joint. If it's really strong but you can't move it, what's the point, right? So for those of you that do a lot of OTA and PTA, you're going to see the hand surgeons casting or splinting people like this. And when you design casts and splints, there's a reason you want that joint at an angle and not perfectly straight. Also, so you can somewhat use it if you wanted to pick something up and drink, but that's not the real reason. We don't want that tissue to scar down. All right, we only have a few more left and I'm going to wrap up this video. So So The next one on the list is a saddle type joint. Well, if you think about a saddle that you put on a horse, the top of the saddle is kind of dished out or has a fossa, and if you set something in that saddle, we call that a saddle joint. There's not a lot of good examples of saddle joints, but what we call the first CMC joint, the first carpometacarpal joint. When you see CMC, it means carpo. Metacarpal. There's a word. But that's the joint between the first carpal bone and the first metacarpal bone. And if you look at that joint, it looks something like this. It's a really good example of a saddle joint. Now, the next one on the list is a gliding joint. Now, a glide joint... It's simply where two bones can glide across each other or sliding joint. I think of gliding as sliding. These aren't going to do extension and flexion. They're not going to do rotation. They're going to glide across each other. So it's a joint where two flat surfaces can glide across each other. And two good examples, one would be your AC joint, where the acromion is and where the clavicle meet. If you move your shoulder around and you put your fingers on it, you can feel those two bones kind of gliding across each other as you move your shoulder around. Another good example would be the TMJ. It can fall under a number of categories. It's a condyloid joint, but it's also a gliding type joint. You can glide your mandible side to side and even slide it forward like if you bit your upper lip or slide it back by your lower lip. It would be gliding. And then the last example that I think we have is called a hinge joint. In a hinge joint, it acts like a door hinge and usually the motion is flexion and extension. These joints can involve flexion and extension. Flexion is when you decrease the angle between bones and extension is when you increase the angle between bones. And some good examples in our elbow. We have what's called the humeral ulnar joint. So we looked at the humeral radial joint or radial humeral joint, but if I have the capitulum here and the trochlea here, then if I looked at the trochlea from a side view, it would be shaped something like that. If I turn the elbow from an anterior view to a lateral view, and you can see... that the trochlear notch with the olecranon process and coronoid process fit around the trochlea so that makes a really good hinge type joint there's a lot of other hinge type joints in the body your knee is an example even though it's a condyloid joint it acts like a hinge and the mandible can hinge so we have three really good examples the elbow the knee and your mandible okay You can see how the mandible falls under a number of categories, but some of these joints have multiple categories as well. Now I know that's probably not the clearest description. Really the best way to go over these is to look at the pictures in the book and watch a couple of other videos where they actually have people demonstrating the motions and we're going to do some of that in another video. So I hope you guys have had as much fun as I had. I hope you gained some understanding about the joints and see how we can name different joints based on the bones that are there. So, if you're in my class, we covered page 47. If you're not in my class, well, I hope you learned something. I'll see you in the next video. We only have another video or two left and we'll be done with the bone section. Thanks for watching. See you soon.

I want you all to learn what's in my note set, what's in the textbook that we use, and what I write on the board. If you're not enrolled in my class, your instructor may cover more information on some subjects, less information, or even totally different subjects than I cover. Please learn the material that your instructor requires you to learn.

Now, hopefully, my videos help you understand the more difficult subjects that you're going to be learning. material. So I'm trying to set a broad foundation where we can add details instead of just puking out all sorts of information.

So if you find them helpful please hit like and or subscribe but definitely like the videos so that if I get enough feedback I know to continue to do them. Because we're in the pandemic these are done very quickly and crudely with my cell phone and me and a board. I hope to be able to make them a little bit sharper and nicer and more professionally done in the future. If I get enough likes, I'm going to invest in that endeavor.

Anyway, we've been covering the skeletal system in Part 1 A&P. We've talked about the shapes of bones. function of bone, different types of ossification, bone growth and length and diameter.

We've talked about fractures and fracture repair and the effects of nutrition and exercise and diet on our bone formation and hormones. So everything in our textbook that we use is in chapter seven. We're not skipping chapter eight and nine. That's what we're doing in lab, which is the different bones of the body and all the landmarks that you have to learn for the laboratory. So we're going to jump to chapter 9 now.

We're going to start covering articulations. If you're following along in my notes, we're going to be on page 47 and 48. So, when it comes to an articulation, you should know the definition of the word articulation. Articulation simply means a joint.

A point in the body where two or more bones come together and form some kind of joint, where they're joined together. Where they communicate. To articulate means to communicate, and to be articulate means that you communicate very well.

So an articulation is a joint. communication between bones. Now most of the joints we think of are freely movable like your fingers and your wrist and your elbow and shoulder and other joints but there are some you may not be aware of and by the way before I get any further anytime you see the root word arthro anywhere in literature or in a report it's referring to the joint. When someone has arthritis it's inflammation itis of a joint. Arthrotic implants are implants into a joint.

So anytime you see arthro, you're talking about joints. Now, when it comes to joints, joints can be classified in a number of ways. One way that we categorize or classify joints is based on their function.

How much movement is in the joint. Another way that we can classify them is through how they are structured or put together, which is an extremely complex process. And I wish we had more time to go into it. For those of you that are going to do things like physical therapy assistant and occupational therapy assistant, or who are going for physical therapy and occupational therapy school or chiropractic school.

We don't have a lot of time for that, so I'm going to try to set the fundamentals. But joints can be very difficult to classify. based on their structural assembly, okay? Because, you know, some of the joints are just extremely complex.

But nonetheless, we're going to do our best, all right? So, if you're following along in the note set, at the top of the first page of this section, there's a little three-row and three-column table that asks you to classify joints based on their function. So when it comes to functional classifications of a joint, There's really only three major classifications, okay? One is called a synarthrosis. Syn means width, and arthro means joint.

And if you're following along in the table, we consider these to be a bony fusion. Or actually, it's not really always a bony fusion. When we say synarthrosis, what we mean is little... or no movement in the joint.

And it really is almost no movement. Okay? These are joints that are fused together. They can be fused with bone, or they can be fused with some cartilage or connective tissue, but there's not a lot of movement in them.

That's why the two bones are with each other. A good example of this... When it comes to this column on the table where you get some examples, one of those would be the sutures of the skull.

Your skull bones, especially the calvaria or cranium, they fuse together and there's no movement there. Or if you look at the os cocci, the three bones of the os cocci that fuse together, there's no movement there. So there's a couple of examples that I can ask, right?

Which would be a good example of a synarthrosis or in a synarthrosis, how much movement is there? Okay, now I'm going to write the next one down, but I'm going to skip it for a moment and do the last one of the three. There's amphiarthrosis. Amphi means a little of both, like an amphibian from bio to live, and amphi both.

They live both on land and in the water. And then there's a diarthrosis. So I'm going to do this one first for a reason. In a diarthrosis, these are said to be freely movable joints.

It's two bones that are free or independent of each other that move together. And think of a diarthrosis as most of the joints in the body that we think of. So I'm not going to write them all down, but it would be fingers, wrist, elbow, shoulder, your hip, your knees, your ankles, your toes. Most of the joints that we think of, and a lot of the vertebral joints, intervertebral joints, not all of them, but most of them, are a diarthrosis where two bones are moving independent of each other. and antheroarthrosis is somewhere between the two and so these have some movement and i tend to think of these as those that kind of wiggle a little bit they're not freely independent but they can wiggle next to each other or move just a little bit.

We have lots of examples of this you can list the knees and the elbows and shoulders and hips. For the amphiarthrosis this would include a few of these. One of my favorites is called the AC joint and AC stands for acromioclavicular joint. Now I'm going to abbreviate joint as a JT.

You can name any joint in the body by taking either the more proximal or more medial bone, or the bone that does less movement, and the bone that does more movement. And so when we move our shoulder around... the clavicle is moving a whole lot and so we call this the acromioclavicular joint where the acromion process and the end of the clavicle come together. If I were to look down on top of this, I would see the spine of the scapula forms the acromion process and then the clavicle comes along here does this and there's a little band of connective tissue across there that lets those two things glide across each other okay so that's one good example another good example is what is called the tib fib joint which stands for tibiofibular joint okay Or I could have what's called the glenohumeral joint or the, you know, femoro-tibial joint.

We can name any joint by naming the two bones or the two or more bones that form it. The tib-fib joint is the joint between the tibia and the fibula. So it's called the tibio-fibular joint or tib-fib joint.

And if I were to look at these two bones, then if I have the proximal tibia and the distal tibia, along with the fibula next to it, There's a little bit of connective tissue here. And if you rotate on your knees without moving your feet, those two bones can kind of move a little bit, but they're not independent of each other. So they are usually bound by some kind of connective tissue that allows a little bit of wiggling. So it's almost as if someone tied your elbows and your hands together, you could still wiggle your arms a little bit.

So those would be called an amphiarthrosis. So know these two examples for synarthrosis, these two examples for an amphiarthrosis, and know several examples for a diarthrosis. arthrosis.

Now, each one of these categories, functional categories, can be broken up into several structural categories based on how the joint is put together and also how it kind of functions. So now, we're going to... to go into the structural classifications of joints and I'm not going to write all of this stuff on the board because a lot of it is filled in in my note set okay I'll fill in a little bit of the information with you but if you were following along in my note set for those of you enrolled in my class we've taken the three functional categories and broken them out on this table and then there's a whole bunch of the structural classifications within those functional categories So for example, synarthrosis has three examples. There's a fibrous connection, and there's a cartilaginous connection, and then there's a bony fusion.

These are fused joints, and are they fused with connective tissue? Are they fused with bone or are they fused with cartilage? So if I go through them, one of the fibrous connections between bones would be called a gomphosis.

Now I'm just going to be honest with you guys. I probably shouldn't say this for those of you enrolled in my class, but I don't really like the way that our textbook does this because several of the joints can fall under different categories depending upon the type of bone. How the joint is put together and also sometimes dependent upon the stage of development. For example, when our suture bones of our skull are growing together and they haven't interlocked and fused, there's some connective tissue, the fontanelles that hold them together.

And so the sutural type joints can have some fibrous connective tissue between them and they have very little movement. When it comes to what's called a gomphosis, a gomphosis is the periodontal ligament. That's the ligament at the base of each tooth. This is one of the ones I think people should know. When you're looking at the jaw, if I could look down at an angle at the top of the jaw and rip the teeth out, then you would see these little air pockets and for example your front teeth would sit in there with their root like this.

And when you slide the tooth into the bone, There's a little piece of connective tissue that holds the tooth to the bone tissue in here. And those ligaments that go around the tooth happen to be called a periodontal ligament. And there is a little bit of wiggle. I mean, if you grab your tooth and wiggle it, it'll move a little. Please don't do that.

It will loosen those ligaments and cause your teeth to fall out earlier in life, which is why you should never open things with your teeth. There's two problems. One, you scratch up the enamel and chip that up and damage the tooth. The other is you can weaken the periodontal ligaments.

But we call this a gonphosis. And it's the ligament between the teeth and the mandible or the maxilla. And it is a type of synarthrosis.

It's a type of fibrous connective tissue that's called a gonphosis. So if I ask you what is a gonphosis, it's the periodontal ligament around your teeth. And it's a type of synarthrosis. one of the ones that's a cartilaginous connection is called a synchondrosis.

And this is when you have cartilage between two bones. But usually in a synchondrosis, I'm going to write something out because I want you to pay attention to this and know it. But when we talk about a synchondrosis, that is usually hyaline cartilage. between two bones and they have almost no movement. Some examples of this would be the growth plate during development or between the sternum and ribs and those cartilages happen to be called costal cartilages.

The term cuesta means rib, and so the costal cartilages where our bones, where our ribs join our sternum, allow a little bit of movement, but not much. And at the growth plates when our bones are developing, if I have the diaphragm... epiphysis and the epiphysis here, that growth plate is hyaline cartilage. And there should be very little to no movement there. We call that a synchondrosis.

And one of the things is that they have hyaline cartilage connecting two bones. those two examples. Okay now if I follow along on the list the next one would be a bony fusion which is called a synostosis and if you look at the name it tells you chondrosis is cartilage, ostosis is a bony fusion. This is where bones are completely fused together and again good examples of this would be the sutures of the skull and the os cocci.

These bones are completely fused together, especially as an adult our sutures have completely grown together. And so we call that a synostosis. It's a bony fusion.

Now all of these are synarthroses, meaning no movement. The next... category we talked about was an amphiarthrosis and under amphiarthrosis there's a number of different types of subcategories and I'm going to talk about a few of them the ones I read on the board are the ones you should at least in my class you should really pay attention to so when it comes to an amphiarthrosis they can be bound with some fibrous connective tissue or with some cartilage and so One of the ones that's got some fibrous connective tissue in it is called a syndesmosis. A syndesmosis has collagen fibers or fibrous connective tissue, okay?

There's usually a substantial ligament holding these two bones together. They almost always involve what we call would be a ligament. Now, some examples of that I've already given you.

We talked about the AC joint, and we've talked about the tib-fib joint. Those would be examples of a syndesmosis, where there's a fibrous band of connective tissue holding the joints together. And the cartilaginous version of an amphiarthrosis would be called a symphysis.

And there's one really good symphysis in the body. And one of the keys to this is that this has fibrocartilage holding the joint together. These are fibrocartilage. If it's hyaline cartilage, then we call that a synchondrosis.

If it's a symphysis, it's fibrocartilage. And the best example is the pubic symphysis. Okay?

Where the os coxi come together at the pubic bones. You would have the obturator foramen here, okay? There's some fibrocartilage holding this together that makes it a very strong but somewhat flexible joint, okay? So that would be the symphysis.

The remainder of the... the types of joints I'm going to cover are all called diarthroses, freely movable joints. And there's a whole bunch of those.

And these are probably the ones that most of y'all, especially if you go into any kinesthetic type of therapy like OTA. and PTA you're going to be dealing with some of these joints okay so I'm going to run through their categorizations and give examples and that's where the questions will come from on exams and state boards so you need to know this information so these are all also classified as synovial joints because they have a synovial membrane that surrounds them and are filled with synovial fluid which lubricates them and provides some shock absorption okay so the first one that's on our list is called a ball and socket joint. And when we talk about a ball and socket, what we're really talking about is a head and a cup.

There's two really good examples of these. In our shoulder, we have what's called the glenohumeral joint. And I didn't write humeral out very well. It's glenohumeral joint, okay, from the humerus of the body.

So the glenoid cavity, if you look at the scapula, it has the glenoid fossa and the head of the humerus. of your shoulder make what's called the glenohumeral joint. There's a whole fibrous capsule that surrounds that.

So that's one example of a head in a cup. The other example would be your hip and that would be called the acetabulofemoral joint. Now this would be the scientific name the acetabulofemoral joint.

So if you study the bones in lab you know that the femur has a head on it. We would have the greater and lesser trochanters. We've covered that anatomy in lab. And then you have the acetabulum of the os coxi where it fits.

So it's a head in a cup. Those are two examples of what's called a ball and socket joint. Now, when we talk about joint movement, the joints can move in what we call an axis.

If they move... in one axis or one direction only it's called a monoaxial joint. Mono meaning one.

If they can move in two directions or two axes then it's called a diaxial joint. If they can move in three or more directions it's called a triaxial joint. Your shoulder is triaxial in the sense that it can move in a number of directions and a number of planes at all these different angles and it can move sort of in a cone shape.

So these ball and socket joints usually have the most or the largest range of motion. Now the next one that's listed by the way is a pivot joint. Well if any of y'all ever played basketball you know what pivot means. If you stop dribbling and you pick up the ball you can only move one foot the other foot has to be planted on the floor so you can move in circles call that pivoting and so these have a rotational motion but they only rotate in one axis like spinning you know a good example of this would be c1 and c2 between the Atlas and the axis if you recall the axis of the vertebrae has this little ball sitting on top called the dens and the atlas wraps around that and it allows you to rotate your head or pivot so c12 or the adlo axis joint is a good example of a pivot joint another one is part of your elbow but what we call the radio humeral joint And some books call it the humeroradial joint and that's okay. Where the end of the humerus is, we have the lateral epicondyle, we have the capitulum, we have the trochlea, and then we have the medial epicondyle.

Well the head of the radius fits right here and so the radius allows you to pronate or supinate or pivot your forearm. That would be a pivoted pivot type joint okay. Those are two good examples and you should know those.

The next one on the list is a condyloid joint. Condyloid joints can go by a number of names and oftentimes people will often refer to these as well as a cam joint. I've heard it both ways in the field of orthopedics.

But these involve condyles. Wherever you have a condyle on a bone, like the mandibular condyle or the femoral condyles, You have a condyloid joint, okay? You also have them where our fingers are.

So, some good examples would be the, what we call the temporomandibular joint, also referred to as the TMJ for those of you who do dental hygiene. Between the temporal bone and the mandibular bone, there's a joint and there's some cartilage there. When you grind that cartilage off from grinding your teeth, or be called what's called a bruxer, when you grind your teeth at night, you're wearing that cartilage out and you get what's called TMJ disease or arthritis in the temporomandibular joint. Another good example would be our knee and it would be called the femorotibial joint.

The condyles of the femur fit on the condyles of the plateau of the tibia. So we call that ephemero-tibial joint or their condyloid. And also between your phalanges, the what we call the IP joints. If you ever hear that term what it means is inter-phalangeal joints.

Now if you take a good look or actually I should say it's the CMC joints. The carpo, oh no, I'm getting that wrong. Please forgive me. I'm trying to think of the right joint in the hand. It's the metacarpophalangeal joint.

Sorry, I worked for a hand surgeon. I should know this, right? MP stands for metacarpophalangeal joints. So if you look at the ends of the metacarpals, they kind of do this. They have a condyle, and the phalanges sit on that like this.

And as you flex your finger, if you keep your finger straight, but you bend them at the MP joint, the metacarpophalangeal joint, they can do this. Now one of the things about condyloid joints or cam joints, if you fracture a bone, You don't want to usually under 99% of the circumstances, you don't want to cast the joint straight. For example, if someone has a cast on their hand, you usually see the wrist like this and the fingers are bent like this instead of straight. When someone has a fractured leg and they cast the knee, they almost never completely cast the knee, at least for long periods of time, straight. It's always got a little bit of a bend in it.

And the reason is this, the distance from this point where the... where the ligaments attach to here is shorter and the ligaments are a little more slack. If I flex my fingers this distance from here to here here is increased now. It might only be that long there, but when I increase it, it tightens those ligaments. And a quick experiment that you can do is if your finger is straight, you can wiggle your finger back and forth like this.

But if I bend my finger a little bit, it becomes much more difficult to wiggle that joint. The joint becomes tighter because I've stretched that ligament that's holding it together. Now, if I casted it straight, While I cast it, a lot of times the connective tissue will also tighten up and then you can't flex your fingers. You lose range of motion. It's very difficult to get that back.

So that's why people will cast certain joints at an angle and it's usually a cam joint or a condyloid joint. You want to be somewhere in the middle of these two so that you don't lose any range of motion. Range of motion of a joint is just as important as the strength of the joint.

If it's really strong but you can't move it, what's the point, right? So for those of you that do a lot of OTA and PTA, you're going to see the hand surgeons casting or splinting people like this. And when you design casts and splints, there's a reason you want that joint at an angle and not perfectly straight.

Also, so you can somewhat use it if you wanted to pick something up and drink, but that's not the real reason. We don't want that tissue to scar down. All right, we only have a few more left and I'm going to wrap up this video.

So So The next one on the list is a saddle type joint. Well, if you think about a saddle that you put on a horse, the top of the saddle is kind of dished out or has a fossa, and if you set something in that saddle, we call that a saddle joint. There's not a lot of good examples of saddle joints, but what we call the first CMC joint, the first carpometacarpal joint.

When you see CMC, it means carpo. Metacarpal. There's a word. But that's the joint between the first carpal bone and the first metacarpal bone.

And if you look at that joint, it looks something like this. It's a really good example of a saddle joint. Now, the next one on the list is a gliding joint.

Now, a glide joint... It's simply where two bones can glide across each other or sliding joint. I think of gliding as sliding.

These aren't going to do extension and flexion. They're not going to do rotation. They're going to glide across each other. So it's a joint where two flat surfaces can glide across each other. And two good examples, one would be your AC joint, where the acromion is and where the clavicle meet.

If you move your shoulder around and you put your fingers on it, you can feel those two bones kind of gliding across each other as you move your shoulder around. Another good example would be the TMJ. It can fall under a number of categories. It's a condyloid joint, but it's also a gliding type joint.

You can glide your mandible side to side and even slide it forward like if you bit your upper lip or slide it back by your lower lip. It would be gliding. And then the last example that I think we have is called a hinge joint. In a hinge joint, it acts like a door hinge and usually the motion is flexion and extension. These joints can involve flexion and extension.

Flexion is when you decrease the angle between bones and extension is when you increase the angle between bones. And some good examples in our elbow. We have what's called the humeral ulnar joint.

So we looked at the humeral radial joint or radial humeral joint, but if I have the capitulum here and the trochlea here, then if I looked at the trochlea from a side view, it would be shaped something like that. If I turn the elbow from an anterior view to a lateral view, and you can see... that the trochlear notch with the olecranon process and coronoid process fit around the trochlea so that makes a really good hinge type joint there's a lot of other hinge type joints in the body your knee is an example even though it's a condyloid joint it acts like a hinge and the mandible can hinge so we have three really good examples the elbow the knee and your mandible okay You can see how the mandible falls under a number of categories, but some of these joints have multiple categories as well.

Now I know that's probably not the clearest description. Really the best way to go over these is to look at the pictures in the book and watch a couple of other videos where they actually have people demonstrating the motions and we're going to do some of that in another video. So I hope you guys have had as much fun as I had.

I hope you gained some understanding about the joints and see how we can name different joints based on the bones that are there. So, if you're in my class, we covered page 47. If you're not in my class, well, I hope you learned something. I'll see you in the next video. We only have another video or two left and we'll be done with the bone section. Thanks for watching.

See you soon.

Transcript for:Understanding Joints in Anatomy and Physiology

Transcript for:
Understanding Joints in Anatomy and Physiology