 Okay, everybody, Dr. O here, and this video, we're going to talk about the six types of synovial joints. So I introduced them in the last video, we're going to go into some more detail here. So in order, we'll cover the pivot joint, the hinge joint, the saddle joint, the plane joint, which I like to call the gliding joint, the condyloid joint, which I usually call an ellipsoid joint and the ball and socket joint. So let's go ahead and dive in. So first we have the pivot joint, which you'll see here on the left and then some examples. So pivot joints allow, they're a pivot or a rotation, or for a rotation of axis. So they allow for rotation around that axis. So these would be monaxial joints or uniaxial joints. They're freely movable, but only in that one plane. So the best examples of pivot joints, we have the atlantoaxial joint. So remember the atlas is C1 and axis is C2. So as you can see in this picture, the dens or odontoid process of C2 comes up inside of the atlas and then the transverse ligament holds it in place. This allows for all of this rotation that occurs between C1 and C2 in your neck. So that's the atlantoaxial joint, an example of a pivot joint. The other one here would be the proximal radio ulnar joint. So you can see that annular ligament there is actually holding that circular head of the radius up against the ulna. So when I pronate and supinate my forearm, this rotation occurs at the proximal radio ulnar joint. So those are examples of pivot joints, which are monaxial or uniaxial. Next we have the hinge joint, just like a hinge on your door. It is uniaxial or monaxial. It's freely movable, but only in one plane. So hinge joints work just like hinges on a door. You can see some examples I give you here. You have the elbow, so the elbow can flex and extend. It's freely movable, but only in that one plane. I can't get my elbow to go other directions if it does. That's generally a problem. So the elbow is a good example. So with the knee, with flexion and extension, the ankle with dorsiflexion and planar flexion, and then the interphalangeal joints, with which would be my finger and toe joints like that. So those are all examples of hinge joints. Next we have a saddle joint, which kind of looks like two saddles sitting on top of each other or a rider sitting on a saddle. So you have the surfaces are concave in one direction and convex in the other, but that's going to be the shape there. So this allows for these two joints, these two bones to fit together in a way that allows for some special movement. These are going to be biaxial joints. So you can see two examples here in the same picture. The first carpometicarpal joint, so the joint that connects the trapezium carpal bone to the first metacarpal of your thumb. So I can move my thumb in one plane like this, but I can also move it across the palm of my hand. And this is opposition. I have an opposable thumb, which allows me to grasp tools and do things like that. So opposition is the movement of my thumb across my palm, towards my pinky finger, and reposition will be bringing it back. So the first carpometicarpal joint is a biaxial joint and it's a saddle joint there. That's really going to be the only key example you need to know, but it's clearly a very important one. If you ask me what makes human special, I mean our huge frontal lobe and our opposable thumbs are the reason that we've dominated this planet. So that's a real good example there. All right. Next we have plane or gliding joints. These are going to be classified as either non-axial or multi-axial because they can move in very few directions or in all directions. It really depends on the joint and depends on the ligaments holding them together. So there really aren't any that move in all directions, but that's kind of how they're classified, multi-axial or non-axial. I call these gliding joints because the movement it really is a gliding movement. Key examples clearly are the intercarpal joints and the intertarsal joints. So the bones of your wrist and ankle as you move, like I have a wrist injury. So I know what kind of movement occurs in my wrist with just normal day-to-day movements. So these gliding movements that occur between the bones of your wrist and your ankles, intercarpal and intertarsal joints are going to be examples of plane or gliding joints. The other example is the acromio-clavicular joints where the clavicle meets with the acromion of the scapula. That would also be a gliding joint. Okay. So those are plane or gliding joints. Next we have the ellipsoid or condeloid joints. So the book calls them ellipsoid. That's fine, but I like to use the term condeloid joints. These are going to be biaxial joints. And the best example is going to be your metacarpophalangeal joints. So the thumbs are separate one. It's a saddle joint. But the knuckle joints here or the joints between your metacarpal and your proximal phalanges is going to be the metacarpophalangeal joints. And because of this condeloid or ellipsoid shape, they are biaxial, meaning that I can bend, I can bend my fingers, flex and extend my fingers like this, but I can also move my fingers in a second direction. So the metacarpophalangeal joints would be the best example of an ellipsoid or condeloid joint. Another good example you can also see in this picture is the radial carpal joints. So between the radius, which is on the thumb side of your hand and the wrist. So being biaxial, I can flex and extend. I can also move my wrist this direction just not very well because of my wrist injury. So that's going to be ellipsoid or condeloid joints being biaxial joints. All right, then we have the ball and socket. So there are only two ball and socket joints in your body. That's going to be the glenohumeral joint or your shoulder joint. And it's going to be your hip joint. These joints have the greatest range of motion in the body, which makes them less stable, especially the shoulder. So the ball and socket joint is a triaxial or multi-axial joint. They're freely movable in all planes. So you can see the hip joint, that's going to be the ball is going to be the head of the femur. The socket's going to be the acetabulum there in the pelvis. With the glenohumeral joint, the head of the humerus will be the ball. The glenoid fossa or glenoid cavity is going to be the socket. Now the shoulder is not really a true socket. So you'll see as we learn more about the shoulder in the future. The shoulder is held together by soft tissues and muscles in a way that the hip doesn't have to be. The hip is held together by this deep bony socket and then the tough ligaments in the hip. Without muscles, you could almost stand up just with the stability in the hip joint itself. The shoulder joint, not the case. Muscles are constantly active to keep to help stabilize the shoulder, which is a great example looking at these two joints of how you sacrifice stability for mobility. So the shoulder is more mobile, less stable, hip less mobile, more stable. All right, so that's going to be the ball and socket joint. So that should be all our examples. Those are the six different types of synovial joints. I hope this helps. Have a wonderful day. Be blessed.