Definition

Noun: 1. A type of synovial joint where movement is limited to rotation around a central axis. This joint allows a bone to turn or pivot within a ring formed by another bone or a ligament. The technical anatomical term is a "pivot joint."

Usage

The term "rotary joint" is primarily used in anatomical and biomechanical contexts to describe a specific, freely moving joint structure. * The joint between the first and second cervical vertebrae (the atlas and axis) is a classic example of a rotary joint, allowing the head to rotate side-to-side. * In engineering, the design of a robotic arm often mimics the function of a biological rotary joint.

Advanced Usage

• Anatomical Synonym: In formal anatomy, "rotary joint" is synonymous with "pivot joint" or "trochoid joint." The latter is a more technical term derived from Greek.
  • The proximal radioulnar articulation is a pivot joint (rotary joint) that enables the rotation of the forearm.

Variants and Related Words

• Pivot Joint (n.): The standard anatomical term for a rotary joint.
• Synovial Joint (n.): The broader category of freely movable joints to which rotary/pivot joints belong.
• Rotation (n.): The specific type of movement permitted by a rotary joint.
• Axis (n.): In anatomy, the second cervical vertebra (C2), which forms a crucial rotary joint with the atlas (C1).

Synonyms

• Pivot joint
• Trochoid joint (technical)
• Rotatory joint

Related Phrases

• Joint of Luschka: While also a pivot-like structure in the cervical spine, this term usually refers to uncovertebral joints, which are not classic synovial rotary joints. The comparison is sometimes made due to the rotational function they facilitate.

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