animal anatomy Anatomy () is the branch of Morphology (biology), morphology concerned with the study of the internal structure of organisms and their parts. Anatomy is a branch of natural science that deals with the structural organization of living things ...

, 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' articulati ...

whose movement axis is parallel to the long axis of the proximal bone, which typically has a convex

articular surface A joint or articulation (or articular surface) is the connection made between bones, ossicles, or other hard structures in the body which link an animal's skeletal system into a functional whole.Saladin, Ken. Anatomy & Physiology. 7th ed. McGraw- ...

. According to one classification system, a pivot joint like the other

—the

hinge joint A hinge joint (ginglymus or ginglymoid) is a bone joint where the articular surfaces are molded to each other in such a manner as to permit motion only in one plane. According to one classification system they are said to be uniaxial (having o ...

has one

degree of freedom In many scientific fields, the degrees of freedom of a system is the number of parameters of the system that may vary independently. For example, a point in the plane has two degrees of freedom for translation: its two coordinates; a non-infinites ...

.Platzer, Werner (2008) ''Color Atlas of Human Anatomy'', Volume 1
p.28
/ref> Note that the

degrees of freedom In many scientific fields, the degrees of freedom of a system is the number of parameters of the system that may vary independently. For example, a point in the plane has two degrees of freedom for translation: its two coordinates; a non-infinite ...

of a joint is not the same as a joint's

range of motion Range of motion (or ROM) is the linear or angular distance that a moving object may normally travel while properly attached to another. In biomechanics and strength training, ROM refers to the angular distance and direction a joint can move be ...

Movements

Pivot joints allow

rotation Rotation or rotational/rotary motion is the circular movement of an object around a central line, known as an ''axis of rotation''. A plane figure can rotate in either a clockwise or counterclockwise sense around a perpendicular axis intersect ...

, 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 Motion, the process of movement, is described using specific anatomical terminology, anatomical terms. Motion includes movement of Organ (anatomy), organs, joints, Limb (anatomy), limbs, and specific sections of the body. The terminology used de ...

and

supination Motion, the process of movement, is described using specific anatomical terms. Motion includes movement of organs, joints, limbs, and specific sections of the body. The terminology used describes this motion according to its direction relativ ...

. 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 ...

, 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 ligamen ...

Distal radioulnar joint The distal radioulnar articulation (also known as the distal radioulnar joint, or inferior radioulnar joint) is a synovial pivot joint between the two bones in the forearm; the radius and ulna. It is one of two joints between the radius and ulna ...

* 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, that can start from C2 To C7. Structure The atlanto-axial joint ...

In contrast, spherical joints (or

ball and socket joints The ball-and-socket joint (or spheroid joint) is a type of synovial joint in which the ball-shaped surface of one rounded bone fits into the cup-like depression of another bone. The distal bone is capable of motion around an indefinite number of ...

) such as the

hip joint In vertebrate anatomy, the hip, or coxaLatin ''coxa'' was used by Celsus in the sense "hip", but by Pliny the Elder in the sense "hip bone" (Diab, p 77) (: ''coxae'') in medical terminology, refers to either an anatomical region or a joint o ...

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