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' articulat ...
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
Degrees of freedom (often abbreviated df or DOF) refers to the number of independent variables or parameters of a thermodynamic system. In various scientific fields, the word "freedom" is used to describe the limits to which physical movement or ...
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 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
* Distal radioulnar joint
* Median atlanto-axial joint
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
{{Authority control
Joints