(triquetral bone) n. a bone of the wrist (see carpus). It articulates with the ulna behind and with the pisiform, hamate, and lunate bones in the carpus.
The joint situated between the arm above and the hand below. The region of the wrist contains eight small carpal bones, arranged in two rows, each containing four bones. Those in the row nearest the forearm are – from the outside inwards when looking at the palm of the hand – the scaphoid, lunate, triquetrum, and pisiform.
Those in the row nearest the hand are the trapezium, trapezoid, capitate and hamate. These latter articulate with the metacarpal bones in the hand and are closely bound to one another by short, strong ligaments; and the wrist-joint is the union of the composite mass thus formed with the RADIUS and ULNA in the forearm. The wrist and the radius and ulna are united by strong outer and inner lateral ligaments, and by weaker ligaments before and behind, whilst the powerful tendons passing to the hand and ?ngers strengthen the wrist.
The joint can move in all directions, and its shape and many ligaments mean that it rarely dislocates – although stretching or tearing of some of these ligaments is a common accident, constituting a sprain. (See JOINTS, DISEASES OF.) In?ammation of the tendon-sheaths may occur as a result of injury or repetitive movement (see UPPER LIMB DISORDERS). A fairly common condition is the presence of a GANGLION, in which an elastic swelling full of ?uid develops on the back or front of the wrist in connection with the sheaths of the tendons. (See also HAND.)... wrist
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