Joint

 
Joint: A joint is the area where two bones are attached for the purpose of motion of body parts. A joint is usually formed of fibrous connective tissue and cartilage. An articulation or an arthrosis is the same as a joint.

Joints are grouped according to their motion: a ball and socket joint; a hinge joint; a condyloid joint (a joint that permits all forms of angular movement except axial rotation); a pivot joint; gliding joint; and a saddle joint.

Joints can move in four and only four ways:

• Gliding -- one bony surface glides on another without angular or rotatory movement;
• Angular -- occurs only between long bones, increasing or decreasing the angle between the bones;
• Circumduction -- occurs in joints composed of the head of a bone and an articular cavity, the long bone describing a series of circles, the whole forming a cone; and
• Rotation -- a bone moves about a central axis without moving from this axis.

The word "joint" comes from the Latin "junctio" meaning a joining (as in a junction).

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