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In human anatomy, the wrist is variously defined as (1) the Carpal bones or carpal bones, the complex of eight bones forming the proximal skeletal segment of the hand; "The wrist contains eight bones, roughly aligned in two rows, known as the carpal bones." (2) the wrist joint or radiocarpal joint, the joint between the radius and the Carpal bones and; (3) the anatomical region surrounding the carpus including the distal parts of the bones of the forearm and the proximal parts of the metacarpus or five metacarpal bones and the series of joints between these bones, thus referred to as wrist joints. "With the large number of bones composing the wrist (ulna, radius, eight carpas, and five metacarpals), it makes sense that there are many, many joints that make up the structure known as the wrist." This region also includes the carpal tunnel, the anatomical snuff box, bracelet lines, the flexor retinaculum, and the extensor retinaculum.
As a consequence of these various definitions, fractures to the carpal bones are referred to as carpal fractures, while fractures such as distal radius fracture are often considered fractures to the wrist.
The radiocarpal (wrist) joint is an condyloid joint formed by the radius and the articular disc proximally and the proximal row of carpal bones distally. The carpal bones on the ulnar side only make intermittent contact with the proximal side — the triquetrum only makes contact during ulnar abduction. The capsule, lax and un-branched, is thin on the dorsal side and can contain synovial folds. The capsule is continuous with the midcarpal joint and strengthened by numerous , including the palmar and dorsal radiocarpal ligaments, and the ulnar and radial collateral ligaments.
The parts forming the radiocarpal joint are the lower end of the radius and under surface of the articular disk above; and the scaphoid, Lunate bone, and triquetral bones below. The articular surface of the radius and the undersurface of the articular disk form together with a transversely elliptical concave surface, the receiving cavity. The superior articular surfaces of the scaphoid, lunate, and triquetrum form a smooth convex surface, the condyle, which is received into the concavity.
Carpal bones of the hand:
In the hand proper a total of 13 bones form part of the wrist: eight carpal bones—scaphoid, lunate bone, triquetral, pisiform, trapezium, trapezoid bone, capitate, and hamate— and five Metacarpus—the first, second, third, fourth, and fifth metacarpal bones.
The midcarpal joint is the S-shaped joint space separating the proximal and distal rows of carpal bones. The intercarpal joints, between the bones of each row, are strengthened by the radiate carpal and pisohamate ligaments and the palmar, interosseous, and dorsal intercarpal ligaments. Some degree of mobility is possible between the bones of the proximal row while the bones of the distal row are connected to each other and to the metacarpal bones —at the carpometacarpal joints— by strong ligaments —the pisometacarpal and palmar and dorsal carpometacarpal ligament— that makes a functional entity of these bones. Additionally, the joints between the bases of the metacarpal bones —the intermetacarpal articulations— are strengthened by dorsal, interosseous, and palmar intermetacarpal ligaments.
The earliest carpal bones to ossify are capitate bone and hamate bone in the first six months of an infant life.
Starting from the mid-position of the hand, the movements permitted in the wrist proper are (muscles in order of importance):
However, movements at the wrist can not be properly described without including movements in the distal radioulnar joint in which the rotary actions of supination and pronation occur and this joint is therefore normally regarded as part of the wrist.
The hand may deviate at the wrist in some conditions, such as rheumatoid arthritis.
Ossification of the bones around the wrist is one indicator used in taking a bone age.
A wrist fracture typically refers to a distal radius fracture. It is more common in non-Hispanic women and is associated with factors such as alcohol consumption, smoking, high serum phosphate levels, osteoporosis, and obesity.
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