palmorientation

Palmorientation is the direction in which the palm surface faces, a fundamental parameter in anatomy, kinesiology, gesture analysis, and sign languages. It describes how the hand is oriented relative to the forearm and body, and it changes with forearm rotation and wrist position. In everyday anatomy, palm orientation is often discussed using the terms supination and pronation.

In anatomical terms, supination occurs when the forearm rotates so that the palm faces anteriorly or upward in the natural standing position. Pronation is the opposite rotation, turning the palm to face posteriorly or downward. Clinically and in biomechanics, additional descriptors may reference the forearm’s axis (radial or ulnar orientation) or describe the palm as facing forward, backward, inward, or outward relative to the body or to a sign space.

In sign languages, palm orientation is a phonological parameter that helps distinguish signs. Orientation can be toward the signer, toward the listener, or oriented in various directions within three-dimensional space. Changes in palm orientation can alter the meaning of a sign even when other articulatory features remain constant, making it a key feature in sign language grammar and recognition systems.

Measurement and representation of palmorientation are typically done through observational coding, motion capture, or sign-language annotation schemes, using discrete categories such as palm up, palm down, palm toward, and palm away, sometimes augmented with lateral (left-right) orientation.

See also: pronation and supination, palmar surface, anatomical position, sign language phonology.