There are six different types of freely movable joints, or diarthroses, in the body.
The gliding joints have articulating bones that are nearly flat. Movement is permitted in a gliding fashion, as shown here.
In a hinge joint, one articulating bone is convex and the other is concave. Their movement is similar to that of the hinge on a door.
The pivot joints permit only one movement—rotation around one axis.
In condylar joints, one articulating bone is oval and convex, while the other is oval and concave. Movement is permitted in a back and forth motion as shown.
Saddle joints have articulating bone surfaces that are both shaped like the seat of a riding saddle. Movement is permitted back and forth, and side to side.
Ball-and-socket joints are the most freely movable joints in the body. One articulating bone is shaped like a "ball," and the other is shaped like a "socket." Movement is permitted in all directions.