Textbooks describe six ways that a synovial (diarthrotic) joint might move:
This joint allows for freedom of rotation as well as back-and-forth movement in all planes. It allows for the most freedom in movement of any other joint. I tried to show this flexibility in the animation, but there's even more flexibilty in movement than I could show.
The drawing tries to show you that the bones can move about one another in many directions-- except that they cannot rotate. Keep in mind that this joint is named for a condyle-containing joint. A condyle is a curved process that fits into a fossa on another bone for its articulation. You also find this type of joint at the mandible-to-temporal bone joint. Think about all the movements we can make with our lower jaw-- we have a lot of flexibility, except we can't rotate our jaw!
Plane (or Gliding) joint:
Although these joints appear to offer a lot of flexibility in movement direction, they do not offer a great distance in movement. But they can move in many directions and they can rotate.
Hinge joints offer ease in movement, but only provide for movement in one plane (no twisting, no sliding side-to-side). Keep in mind that although a good example of a hinge joint is at your elbow, there are two bones in your forearm that interact at the elbow joint. Only one of them, the ulna, makes a hinge joint. When you are in the anatomical position and you bend your elbow as if bringing your palm to your shoulder, that is the movement of the hinge joint. If you instead, from the anatomical position, twist at the elbow so that your palm faces posteriorly, that is NOT the hinge joint (it is a pivot joint, see below).
This joint is one where one bone spins around on another bone. Although only one direction of spin has been diagrammed above, the spinning can occur in either direction. This type of joint is in our elbow (for the twisting motion) and is between our first two cervical vertebrae (as in the figure from your book, this allows for you to shake your head "no").
Most students have a hard time distinguishing this joint from the condyloid joint or plane joint. But it is easy! In the saddle joint, both of the bones that meet have odd shapes, but they are totally complementary to one another. (Remember, in the condyloid joint, one bone is concave and the other is convex). So in the saddle joint, each bone has both concavities and convexities, but they fit nicely.
Every synovial joint fits one of these categories. You will not have to specifically identify each joint of the body as fitting into one or another of these categories. But, you should be familiar with each, and have some idea of which allows for the most movement options. You should also know of an example of each of the six.
Other places to look for joints:
An image of four of the types of joints (ball-and-socket, gliding, hinge, and saddle) is available at Body Online, and then you go from the home page and click on the button underneath all the systems on "images" and scroll down to "Joints and Mechanical Equivalents."
Another website where you can find out more about 4 types of these joints (the movie didn't work for me) is this website from University of Leeds.
Here's a website specifically on the shoulder joint-- and the movies here actually work!
© 2011 STCC Foundation Press