Where two bones meet each other, this junction is referred to as a joint or
The joints of the human skeleton may be characterized, in general, in three
• material holding the joint together
• relative mobility
• degrees of freedom
Tab1 Material Holding the Joint Together
Joints are characterized by the type of material that holds the bones together
at the joint.
If the bones are fused together with bony tissue, the articulation is called a
If the bones are held together by cartilage tissue it is called a synchondrosis.
If the bones are held together by FCT it is called a syndesmosis.
NOTE: A synovial articulation is somewhat different and will be described in detail in
the next section.
Tab 2 Relative Mobility
A second way of categorizing joints of the human skeleton is according to relative
The junctions of some bones are nonmobile, such as a synosteosis.
Others are semimobile, as seen with some syndesmoses.
Being structured to facilitate motion, synovial articulations (see the next
section) are mobile to various degrees.
Tab 3 Degrees of Freedom
The term degrees of freedom refers to the number of planes in which movement
is permitted. This also equals the number of axes around which motion can take place
at a particular joint.
One degree of freedom means that the joint is uniaxial. Motion can take place in a single
plane around one axis only. An example is a hinge joint.
Two degrees of freedom mean that the joint is biaxial. Motion can take place
around two different axes.
With three degrees of freedom, we say that the joint is multiaxial. Motion can
take place around the three axes in all three planes. An example is ball and socket