Classification of Joints - Online Tutor, Practice Problems & Exam Prep

Joints are classified into functional and structural categories. The three functional classifications are synarthroses (immovable), amphiarthroses (slightly movable), and diarthroses (freely movable). Structurally, joints can be fibrous (bound by collagen fibers), cartilaginous (bound by cartilage), or synovial (featuring a synovial cavity). Synovial joints allow dynamic movement, while fibrous and cartilaginous joints offer stability at the cost of mobility. Understanding these classifications is essential for grasping joint function and anatomy.

Introduction to Classification of Joints

In this video, we're going to begin our lesson on the classification of joints. Joints can actually be classified by both their function and their structure as well. It turns out that there are 3 functional joint classifications and 3 structural joint classifications, for a total of 6 classifications. A single joint can be categorized into just one of the 3 functional joint classifications and just one of the 3 structural joint classifications. A single joint can be classified into 2 of these groups.

What this means is that there is overlap between the functional joint classifications and the structural joint classifications. You can see this overlap really nicely in our map of the lesson on joints which we covered in our previous lesson videos. If you haven't yet seen that, you should go check it out. Moving forward in our course, we're first going to talk about the functional joint classifications. In a separate video, we'll talk about the structural joint classifications.

I'll see you all in our next video.

Functional Joint Classifications

In this video, we're going to introduce the functional joint classifications. And so again, there are 3 functional joint classes that are actually based on the amount of movement that is allowed by the joint. And so, notice down below we have these 3 functional joint classes numbered 1, 2, 3. And what you'll notice about each of these functional joint classifications is that they all end with the word arthrosis, which recall from our previous lesson videos is just a term that means joint. Since recall the root arthur or arthro is a root that means joint.

Now, notice that each of these also ends with the letters IS, which is actually the singular form of these classes. However, if we want to convert them to their plural forms, all we need to do is replace the IS with the letters ES. And so, that's how you get the plural forms. Now, the very first functional joint class in our lesson is the synarthrosis. And so, this root syn is a root that means together.

And so, in a synarthrosis, the skeletal elements in that joint are held so closely together that there's very little space or very little room for movement. And so, notice that the S in synarthrosis can remind us that this is going to be a still or stationary joint with basically no movement, especially under normal conditions. And so, these synarthroses are also known as immovable joints. And so, notice that for the symbol that we're using for the synarthrosis, it does not have any kind of movement arrow going around it. Unlike the other two symbols for the other two joint classifications. And so, because it doesn't have any movement arrows going around it, that can hopefully be a helpful reminder to you that the synarthroses are going to be still or stationary joints with basically no movement.

Now, the next functional joint classification in our lesson is going to be the amphiarthrosis. Now, the root amphi is actually a root that means both or both sides. And so, amphiarthrosis generally allow for movement on both sides of the joint. Now, what you'll notice is that the A in amphiarthrosis can remind us that these are joints that are slightly movable joints with just a little or an average amount of movement, if you will. And so, hopefully, the A in a little and the A in average can remind you of the A in amphiarthrosis.

And so, amphiarthroses allow for more movement than synarthroses, which allow for basically no movement. And so, notice that the symbol that we're using for amphiarthroses has just one movement arrow going around it. And so, hopefully that one movement arrow going around the symbol for amphiarthroses can remind you that amphiarthrosis allows for just a little movement or an average amount of movement. Now, it is also worthy of noting that synarthroses and amphiarthroses are often found in the axial skeleton, but they're not always found in the axial skeleton, it's just often. Now, the final functional joint classification in our lesson is the diarthrosis.

And so, the root di or dia in this word refers to through or across. And so, diarthrosis allow for movement through or across the joint. And so, the D in diarthrosis can remind us that these joints have dynamic movement and are freely movable joints that allow for a lot of movement, especially with respect to amphiarthroses and synarthroses. Now, it is also worthy of noting that the amount of movement in these diarthroses can vary. And so, some diarthroses will have more movement than other diarthroses.

But in general, the diarthroses allow for more movement than amphiarthroses, and amphiarthroses allow for more movement than synarthroses. And so, these diarthroses are usually going to predominate in the appendicular skeleton. And the diarthroses are usually the joints that a typical person might think of when they think about a joint. And so it includes joints such as our shoulder joint and our knee joint, for example. And so, let's take a look at this image down below where we can start to piece some things together.

And so, notice over here we have this person with this skeleton, and we are focusing in on specific regions. The first region that we're focusing in on is the skull. And so, what you'll notice is that the sutures of the skull which are highlighted here, essentially these cracks that are in the skull, these are a type of joint. And because these essentially sutures in the skull allow for basically no movement, they are still or stationary and allow for no movement, we know that these sutures of the skull that are highlighted here are going to be synarthroses. And again, the root syn is a root that means together and so notice that the bones of the skull are held so closely together that there's not a lot of room for movement.

And although again, these are considered immovable joints, it is important to note that they basically allow for no movement. And so, what this means is that the sutures of the skull are designed to accommodate the growth of the brain which is really really slow. And so, the sutures do technically allow for some movement but it's not really detectable movement that you would think about on a regular basis, and so they're still classified as synarthrosis and immovable joints, even though technically they still allow for, like the tiniest, like almost unrecognizable amount of movement. But again, the synarthroses do not allow for as much movement as the amphiarthroses. And so, the amphiarthroses, again, that root amphithroses means both or both sides, and so usually it allows for movement on both sides of the joint.

And the A in amphiarthrosis can remind us that these joints allow for a little or an average amount of movement, and so they allow for more movement than the synarthrosis. And again, the one movement arrow going around the symbol is going to be a helpful reminder that these amphiarthroses allow for some movement. And so, an example here are the intervertebral joints that are in our spine, which allow for some movement, allowing us to lean forward and also lean backward as well, and so they do allow for movement on both sides of the joint. And they only allow for a little movement, not as much as the diarthroses. And so, the diarthroses, again, the D in diarthroses can remind us of the D in dynamic movement.

And so they allow for dynamic and free movement. And so, a classic example of a diarthrosis is going to be the shoulder joint. And so, of course, our shoulders allow for a lot of movement through and across the joint. And so, hopefully, this can help remind you of the diarthrosis having a lot of movement. And notice that the symbol has multiple movement arrows going around it.

And because it has multiple movement arrows going around it, that can hopefully remind you that it has dynamic movement. And so this here concludes our brief lesson on the 3 functional joint classifications, and moving forward in our course, we're going to continue to utilize these symbols that you see here to represent these 3 functional joint classifications. And so, I'll see you all in our next video.

Classification of Joints Example 1

So, here we have an example problem that says rheumatoid arthritis causes pain when joints move. Which joint type is most likely affected? And we've got these four potential answer options down below. Now, the biggest clue we have here in this problem is that it says rheumatoid arthritis causes pain when joints move. Now, when we're classifying joints based on their movement, that leads us to the functional classes of joints, which recall are the synarthroses, amphiarthroses, and diarthroses.

Which are all listed here as potential answer options. Now, recall that synarthroses are still or stationary joints that do not move. So, these are also known as immovable joints. And so, if we're thinking about joints moving, it's not going to be the synarthroses. And so for that reason, we can eliminate answer option a.

And if we can eliminate answer option a, that also means we can eliminate answer option d, which says that all 3 functional joint classes are affected. And so, now we're between option b, amphiarthroses, or option c, diarthroses. And again, when we are thinking about movement it's the diarthroses that allow for dynamic movement. And so, option c is going to be the correct answer for this example. Amphiarthroses recall only allow for a little movement.

And so, it is true that rheumatoid arthritis is an autoimmune disease that affects diarthroses, or joints that have dynamic movement. And so because that's the case, that concludes this example, and I'll see you all in our next video.

Which of the following statements is false?

• A. All amphiarthroses are in the axial skeleton.
• B. All diarthroses allow for a greater range of motion than all amphiarthroses.
• C. Synarthroses can allow a small amount of movement.
• D. Arthritis is a common disease associated with joints.

Structural Joint Classifications

So, now that we've covered functional joint classifications in our last lesson video, in this video we're going to introduce the structural joint classifications, and talk about how those functional joint classifications overlap with these structural joint classifications. And so, there are also 3 structural joint classes and these structural joint classes are based mainly on the binding material that is used between the skeletal elements to join those skeletal elements together in these joints. Now, notice down below we have listed the 3 structural joint classes that are numbered 1, 2, 3. And so, they are the fibrous joints, the cartilaginous joints, and the synovial joints. And so, in the fibrous joints, as their name implies, the skeletal elements are going to be bound by collagen fibers of dense connective tissue.

Which recalls a type of fibrous connective tissue or a type of connective tissue proper. And the type of dense connective tissue that is usually used in these fibrous joints is dense irregular connective tissue. And we'll be able to see that as we move forward in our course and talk more about these fibrous joints. Now, recall from our previous lesson videos that the collagen fibers provide a lot of strength. And so, the strength of these collagen fibers makes fibers joints very stable joints.

But recall that the stability of a joint comes at the cost of the mobility of the joint. And so, fibrous joints have limited mobility and therefore, they are always going to be classified either as synarthroses or amphiarthroses, which are types of functional classifications from our previous lesson videos. And that's why we have the symbol for synarthroses and the symbol for amphiarthroses over here. And so recall that the synarthroses because the symbol does not have a movement arrow going around it, it can remind you that the synarthroses are going to be still or stationary joints that basically allow for no movement and are generally considered immovable joints. And, Amphiarthroses notice the symbol has just one movement arrow going around it.

Which reminds you that they allow for a little or an average amount of movement if you will. And so, both synarthroses and amphiarthroses are going to be limited in their ability, for mobility or movement. Especially in comparison to diarthroses, which allow for dynamic movement. Now, the 2nd joint classification, structural joint classification in our lesson are the cartilaginous joints. And as their name implies, the bones are going to be bound by cartilage.

Either hyaline cartilage or fibrocartilage. But elastic cartilage usually does not have a huge role in these cartilaginous joints. Now, the cartilage in these cartilaginous joints is going to provide stability to the cartilaginous joints. However, once again, the stability of the joint comes at the cost of mobility. And so, like the fibrous joints, these cartilaginous joints are always going to be classified either as synarthroses or amphiarthroses.

Which is why we have the symbols there. Now, the 3rd and final type of Structural Joint Classification in our lesson are the Synovial Joints. And the synovial joints are characterized by having a synovial cavity or a synovial space. Space in between the bones of the synovial joint and ligaments within an articular capsule. And so, later in our course, we're going to talk a lot more about these synovial joints including the synovial cavity, the synovial fluid that they contain, and this articular capsule as well.

But for now, what you should note is that these synovial joints allow for dynamic movement or free range of movement. And so, that means that they are always going to be categorized as diarthroses, which is why we have the symbol for diarthroses here in the lesson. And so, notice that the symbol for diarthroses has multiple movement arrows going around it, which reminds us that diarthroses have, dynamic movement. Now, it is worthy of noting once again that the synovial joints which are categorized as diarthroses can vary in the amount of movement. And so, some synovial joints will allow more movement than other synovial joints.

But again, we'll get to talk more about this as we move forward in our course. For now, let's take a look at our image down below, where we can see a few examples. And so notice over here on the left hand side, we've got the skeleton of this person and we're focusing in on these specific regions. The first region that we're focusing in on is down here on the distal end of the tibia and the fibula of the leg, the lower leg. And so, what you'll notice is over here we have the tibia and here we have the fibula.

And what you'll notice is that, right here in this region on the distal end is a fibrous joint. And we're zooming in here to show you the fibers of this fibrous joint. And again, usually the, fibers of the fibrous joints are going to be of dense irregular connective tissue where the fibers are going to have an irregular or random arrangement of fibers in the extracellular matrix as you can see here. And so, these fibers joints again, they provide a lot of stability, but that comes at the cost of mobility and that's why they're always going to be classified either as synarthroses or amphiarthroses. Now, for the cartilaginous joint, we're focusing in on the spine.

And so, in the spine, there are these intervertebral joints, these intervertebral disks. And in between them are going to be fibrocartilage. And so this is a type of cartilaginous joint. And so, notice zooming in here, we can see the image from our previous lesson videos showing cartilage. And so you can see the chondroblast and the chondrocytes that we talked about from our previous lesson videos on cartilage.

And so, with these cartilaginous joints, again they provide a lot of stability like the fibrous joints can. However, the stability comes at the cost of mobility. And so, like the fibrous joints, they're always classified either as synarthroses or amphiarthroses. And then last but not least, in this person over here we're focusing in on the hip joint. And in the hip joint, that is going to be an example of a synovial joint.

And so, here you can see the femur is coming into contact with the pelvis here at this joint and in this joint, what you'll notice is that there is a synovial cavity, which is this space that you can see right here and it's also going to contain an articular capsule, which is essentially this structure that you can see going around it made of dense irregular connective tissue. And again, we'll be able to talk a lot more about these synovial joints as we move forward in our course. But the synovial joints are usually going to be the joints that most people will think of when you think about joints. So, they include our shoulder joint which has a lot of dynamic movement, our elbow, our knee, our hip joints for example, and there are many others as well. And so, this here concludes our brief lesson on structural joint classifications and as we move forward in our course, we'll be able to learn a lot more about each of these, learn a lot more about each of these types of joints and examples of these types of joints.

And we'll also be able to get some practice applying these concepts. So, I'll see you all in our next video.

Classification of Joints Example 2

So, here we have an example problem that says, how would you classify a joint that uses cartilage to join bones together and is slightly movable? And we've got these 4 potential answer options down below. Now, of course, a joint that uses cartilage to join bones together must be a cartilaginous joint. And so that means that we can eliminate answer option A, which says fibrous joint, and answer option C, which also says fibrous joint. And now we're limited to either option B, cartilaginous synarthrosis, or option D, cartilaginous amphiarthrosis.

And so, recall that a slightly movable joint is going to have a little movement. And so, that also reminds us that it's going to have an average amount of movement, if you will. And so, the A in "a little" or the A in "average" can remind us of the A in amphiarthrosis. And so, of course, this slightly movable part tells us that this must be an amphiarthrosis. And so, notice option D says cartilaginous amphiarthrosis, which is the correct answer.

And option B says synarthrosis, but synarthroses are generally considered immovable. And so, for that reason, we can eliminate option B. So that here concludes this example, and I'll see you all in our next video.

Which of the following joint classifications is not based on the joint's range of motion?

• A. Synovial.
• B. Diarthroses.
• C. Amphiarthroses.
• D. Synarthroses.

Here’s what students ask on this topic:

What are the three functional classifications of joints?

The three functional classifications of joints are synarthroses, amphiarthroses, and diarthroses. Synarthroses are immovable joints, meaning they allow for little to no movement. Examples include the sutures in the skull. Amphiarthroses are slightly movable joints, allowing for a limited range of motion. An example is the intervertebral discs in the spine. Diarthroses are freely movable joints, permitting a wide range of movements. These include joints like the shoulder and knee. Understanding these classifications helps in grasping how different joints contribute to body movement and stability.

What are the three structural classifications of joints?

The three structural classifications of joints are fibrous, cartilaginous, and synovial joints. Fibrous joints are connected by dense connective tissue, primarily collagen, and are generally immovable or slightly movable, such as the sutures in the skull. Cartilaginous joints are connected by cartilage, either hyaline or fibrocartilage, and allow for limited movement, like the intervertebral discs. Synovial joints have a synovial cavity filled with fluid, allowing for free movement. Examples include the shoulder, hip, and knee joints. These structural classifications help in understanding the composition and function of different joints in the body.

How do synarthroses differ from diarthroses?

Synarthroses and diarthroses differ primarily in their range of movement. Synarthroses are immovable joints, meaning they allow for little to no movement. They are typically found in areas requiring stability, such as the sutures in the skull. Diarthroses, on the other hand, are freely movable joints that permit a wide range of movements. These joints are characterized by a synovial cavity filled with fluid, which facilitates dynamic movement. Examples of diarthroses include the shoulder, hip, and knee joints. Understanding these differences is crucial for comprehending how various joints contribute to body mechanics.

What is the role of synovial fluid in synovial joints?

Synovial fluid plays a crucial role in synovial joints by providing lubrication, reducing friction, and facilitating smooth movement between the articulating bones. It is contained within the synovial cavity, a space between the bones of the joint. The fluid also supplies nutrients to the cartilage and removes metabolic waste, contributing to the overall health and function of the joint. Additionally, synovial fluid acts as a shock absorber, distributing stress and reducing the impact on the joint during movement. This makes synovial joints highly efficient for dynamic and repetitive motions.

What are examples of amphiarthroses in the human body?

Examples of amphiarthroses in the human body include the intervertebral discs in the spine and the pubic symphysis. The intervertebral discs are cartilaginous joints that allow for slight movement between the vertebrae, enabling flexibility and shock absorption in the spine. The pubic symphysis, located between the left and right pubic bones, is another cartilaginous joint that permits limited movement, which is particularly important during childbirth. These joints provide a balance between stability and mobility, allowing for essential movements while maintaining structural integrity.