wrist

wrist The joint between the end of the forearm and the hand. Confusion can arise because a ‘wrist’ watch is actually worn above the wrist (it would be both inconvenient and uncomfortable to wear a watch over the joint itself). Movements occur in two planes — flexion/extension and adduction/abduction (inward/outward). This is a relatively complex joint as it is an articulation between the lower end of the long bones of the forearm (radius and ulna) and the eight small bones of the hand (carpal bones). These carpal bones are connected to one another by ligaments so that they form an arch, concave towards the palm, with its ends connected by a fibrous tissue band. Through this ‘tunnel’ run long tendons which control the fingers and, more importantly, the median nerve which carries the nerve supply to some muscles of the hand and to the skin of some of the fingers. This arrangement can present problems; the sheaths of the tendons can become inflamed and swollen thereby compressing the median nerve, leading to loss of sensation of the thumb, index, and middle fingers and loss of fine co-ordinated movements of the thumb (carpal tunnel syndrome). This can result from repetitive movements when using machinery, and the condition has become recognized as a form of industrial injury. Because of the reflex protective outstretching of the hand during a fall, the wrist is a common site of injury, often sprains. Fractures of the ends of the radius and ulna also occur (Colles fracture), particularly in elderly women with osteoporosis.

William R. Ferrell

See also hands; joints; skeleton.