Types of Joints
Freely moveable joints fall into one of several different categories. The different types of
joints are:

Pivot joints (known also as rotary joints). These joints allow for rotation around
an axis. There is a pivot joint near the top of your spine that allows your head to
move from side to side.

Hinge joints. This type of joint can open and close like a door. Your elbow is a
hinge joint. Your biceps and triceps muscles are basically two people standing on
opposite sides of a wall (the humerus, or upper-arm bone), each with one hand
reaching over to its respective side of a door (the bones of the lower arm). The
biceps "shuts" the door, by contracting and lessening the degree of the joint angle,
and the triceps, when it pulls on its respective side of the door, "opens" the door,
as the hinge then widens.

Gliding joints (known also as plane joints). This type of joint features two bone
plates that glide against one another. The joints in your ankles and wrists are
gliding joints. (Holding your forearm steady while your hand points upward and
then waving side-to-side with your hand is an example of this joint's functioning.)

Ball-and-socket joints. This is the most manoeuvrable type of joint. Your
shoulder and your hip are both ball-and-socket joints. These joints feature a
connection between one bone-end equipped with a protrusion that fits into the
receptive space at the end of the other bone in the joint. These joints allow for
forward motion, backward motion and circular rotation.

Saddle joints. These joints allow for two different types of movement. For
instance, a saddle joint allows your thumb to move toward and away from your
forefinger (as when you spread all five digits out, then bring them all together
side-by-side) as well as cross over the palm of your hand toward your little finger.

Conyloid joints. These joints are similar to ball-and-socket joints, just without
the socket (the "ball" simply rests against another bone end).

Types of Joints in the Human Body
The point where two or more bones meet is called a joint. Joints are classified by their structure or
the way they move.
Suture: The joints of the skull are known as sutures (top, left). Sutures do not have a wide range
of movement. Instead, they allow for growth and very limited flexibility.
Hinge joints: (top, right) allow for movement in one plane. The hinge joints of the elbow and knee,
for example, bend up and down.
Gliding Joint: Two flat-surfaced bones that slide over one another make up a gliding joint (bottom,
right). Gliding joints, such as those in the wrist and the foot, provide for limited movement.
Ball-and-socket joints: (bottom, left) allow for the greatest range of motion. The ball-and-socket
joints of the shoulder and hip, for example, can rotate in a complete circle.