In
animal anatomy, a pivot joint (trochoid joint, rotary joint or lateral ginglymus) is a type of
synovial joint
A synovial joint, also known as diarthrosis, joins bones or cartilage with a fibrous joint capsule that is continuous with the periosteum of the joined bones, constitutes the outer boundary of a synovial cavity, and surrounds the bones' articul ...
whose
movement axis is parallel to the
long axis of the proximal bone, which typically has a convex
articular surface.
According to one classification system, a pivot joint like the other synovial joint —the
hinge joint has one
degree of freedom.
[Platzer, Werner (2008) ''Color Atlas of Human Anatomy'', Volume 1]
p.28
/ref> Note that the degrees of freedom of a joint is not the same as the same as joint's range of motion.
Movements
Pivot joints allow for rotation, which can be external (for example when rotating an arm outward), or internal (as in rotating an arm inward). When rotating the forearm, these movements are typically called pronation and supination. In the standard anatomical position
The standard anatomical position, or standard anatomical model, is the scientifically agreed upon reference position for anatomical location terms. Standard anatomical positions are used to standardise the position of appendages of animals with r ...
, the forearms are supinated, which means that the palms are facing forward, and the thumbs are pointing away from the body. In contrast, a forearm in pronation would have the palm facing backward and the thumb would be closer to the body, pointing medially.
Examples
Examples of a pivot joint include:
* Proximal radioulnar joint
The proximal radioulnar articulation, also known as the proximal radioulnar joint (PRUJ), is a synovial pivot joint between the circumference of the head of the radius and the ring formed by the radial notch of the ulna and the annular ligament ...
* Distal radioulnar joint
* Median atlanto-axial joint
The atlanto-axial joint is a joint in the upper part of the neck between the atlas bone and the axis bone, which are the first and second cervical vertebrae. It is a pivot joint.
Structure
The atlanto-axial joint is a joint between the atlas ...
In contrast, spherical joints (or ball and socket joints) such as the hip joint permit rotation and all other directional movement, while pivot joints only permit rotation.
References
External links
Synovial Joints-Pivot Joints
from The University of Michigan Medical School
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Joints