Definition

Noun: A pivot joint is a type of synovial joint in the human body where a rounded or pointed bone process rotates within a ring formed partly by bone and partly by a ligament. This anatomical structure allows movement limited primarily to rotation around a single central axis.

Examples of Usage

• The articulatio trochoidea between the first and second cervical vertebrae (the atlas and axis) allows the head to rotate from side to side.
• In the forearm, the proximal radioulnar joint is a classic example of an articulatio trochoidea, permitting the rotation of the radius around the ulna during actions like turning a doorknob.

Advanced Usage

• Functional Classification: In kinesiology, an articulatio trochoidea is classified as a uniaxial diarthrosis, meaning it is a freely movable joint with one degree of freedom (rotation).
• Clinical Context: Degeneration or injury to an articulatio trochoidea, such as in the atlantoaxial joint, can severely limit rotational movement and cause significant pain.

Variants and Related Words

• Pivot Joint (n): The common English synonym for .
• Trochoid Joint (n): An alternative, less common term derived from the same Greek root ( meaning wheel).
• Rotary Joint (n): A descriptive term emphasizing the joint's function.

Synonyms

• Pivot joint
• Trochoid joint
• Rotary joint

Related Terms (Not Phrasal Verbs)

• Synovial Joint: The broader category of freely movable joints to which the pivot joint belongs.
• Uniaxial Joint: A joint that moves primarily around one axis, like a pivot or hinge joint.
• Rotation: The primary movement allowed by this joint type.

Noun

1. a freely moving joint in which movement is limited to rotation
   • the articulation of the radius and ulna in the arm is a pivot joint