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Anatomy and basic biomechanics of the wrist

Blake Reid Boggess, DO, FAAFP
Section Editor
Karl B Fields, MD
Deputy Editor
Jonathan Grayzel, MD, FAAEM


The wrist is a complex joint that serves as the link between the forearm and hand and is critical for many upper extremity movements. An understanding of wrist anatomy allows for appreciation of the biomechanics of wrist movement, which helps the clinician to understand injury patterns, perform an efficient history and physical examination, and improve diagnostic accuracy and treatment decisions.

This topic will review the anatomy and biomechanics of the wrist. Approaches to the diagnosis of wrist pain and detailed discussions of specific wrist problems are reviewed separately. (See "Overview of carpal fractures" and "Distal radius fractures in adults" and "Scaphoid fractures".)


Orientation and terminology — The anatomic position of the wrist defines the palmar or volar surface as anterior and the dorsal surface as posterior (figure 1 and figure 2). The ulna is considered medial and the radius lateral. The wrist is defined as the distal aspect of the radius and ulna, the eight carpal bones, and their articulations with the proximal metacarpals.

Carpal bones — The carpal bones are divided into two rows: proximal and distal (image 1 and figure 3). The proximal carpal row is composed of the scaphoid, lunate, triquetrum, and pisiform. The distal carpal row is comprised of the trapezium, trapezoid, capitate, and hamate.

The scaphoid, also called the "navicular," is the second largest carpal bone and was so named from the Greek word ‘‘scaphe’’ meaning ‘‘dug-out, trough, or boat,’’ because of its remote resemblance to a boat. It is shaped somewhat like a kidney bean and traverses the midcarpal joint. It has three named regions, including the proximal pole, the distal pole (tubercle), and the waist, which separates the two poles. Over 80 percent of its surface is covered with articular cartilage.

Blood is supplied to the scaphoid by branches of the radial artery [1]. The dorsal scaphoid branch typically enters the dorsal ridge at the level of the scaphoid waist and supplies the proximal 70 to 80 percent of the bone. The volar (or palmar) scaphoid branch of the radial artery enters the more distal tubercle and supplies the distal 20 to 30 percent of the bone. The blood supply to the proximal pole of the scaphoid can be disrupted by a fracture, which increases the risk of delayed union or nonunion (figure 4). (See "Scaphoid fractures".)


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Literature review current through: Sep 2016. | This topic last updated: Nov 17, 2014.
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