Wrist Joint (Radiocarpal Joint)-Movements-Important Relations-Wrist Joint Injuries-Falls on the Outstretched Hand-

Wrist Joint (Radiocarpal Joint)

■■ Articulation: Between the distal end of the radius and the articular disc above and the scaphoid, lunate, and triquetral bones below. The proximal articular surface forms an ellipsoid concave surface, which is adapted to the distal ellipsoid convex surface.

■■ Type: Synovial ellipsoid joint

■■ Capsule: The capsule encloses the joint and is attached above to the distal ends of the radius and ulna and below to the proximal row of carpal bones.

■■ Ligaments: Anterior and posterior ligaments strengthen the capsule. The medial ligament is attached to the styloid process of the ulna and to the triquetral bone. The lateral ligament is attached to the styloid process of the radius and to the scaphoid bone.

■■ Synovial membrane: This lines the capsule and is attached to the margins of the articular surfaces. The joint cavity does not communicate with that of the distal radioulnar joint or with the joint cavities of the intercarpal joints.

■■ Nerve supply: Anterior interosseous nerve and the deep branch of the radial nerve

Movements

The following movements are possible: flexion, extension, abduction, adduction, and circumduction. Rotation is not possible because the articular surfaces are ellipsoid shaped.

The lack of rotation is compensated for by the movements of pronation and supination of the forearm.

Flexion is performed by the flexor carpi radialis, the flexor carpi ulnaris, and the palmaris longus. These muscles are assisted by the flexor digitorum superficialis, the flexor digitorum profundus, and the flexor pollicis longus.

Extension is performed by the extensor carpi radialis longus, the extensor carpi radialis brevis, and the extensor carpi ulnaris. These muscles are assisted by the extensor digitorum, the extensor indicis, the extensor digiti minimi, and the extensor pollicis longus.

Abduction is performed by the flexor carpi radialis and the extensor carpi radialis longus and brevis. These muscles are assisted by the abductor pollicis longus and extensor pollicis longus and brevis.

Adduction is performed by the flexor and extensor carpi ulnaris.

Important Relations

■■ Anteriorly: The tendons of the flexor digitorum profundus and superficialis, the flexor pollicis longus, the flexor carpi radialis, the flexor carpi ulnaris, and the median and ulnar nerves

■■ Posteriorly: The tendons of the extensor carpi ulnaris, the extensor digiti minimi, the extensor digitorum, the extensor indicis, the extensor carpi radialis longus and brevis, the extensor pollicis longus and brevis, and the abductor pollicis longus

■■ Medially: The posterior cutaneous branch of the ulnar nerve

■■ Laterally: The radial artery

Wrist Joint Injuries

The wrist joint is essentially a synovial joint between the distal end of the radius and the proximal row of carpal bones. The head of the ulna is separated from the carpal bones by the strong triangular fibrocartilaginous ligament, which separates the wrist joint from the distal radioulnar joint. The joint is stabilized by the strong medial and lateral ligaments.

Because the styloid process of the radius is longer than that of the ulna, abduction of the wrist joint is less extensive than adduction. In flexion–extension movements, the hand can be flexed about 80° but extended to only about 45°. The range of flexion is increased by movement at the midcarpal joint.

A fall on the outstretched hand can strain the anterior ligament of the wrist joint, producing synovial effusion, joint pain, and limitation of movement. These symptoms and signs must not be confused with those produced by a fractured scaphoid or dislocation of the lunate bone, which are similar.

Falls on the Outstretched Hand

In falls on the outstretched hand, forces are transmitted from the scaphoid to the distal end of the radius, from the radius across the interosseous membrane to the ulna, and from the ulna to the humerus; thence, through the glenoid fossa of the scapula to the coracoclavicular ligament and the clavicle; and finally, to the sternum. If the forces are excessive, different parts of the upper limb give way under the strain. The area affected seems to be related to age. In a young child, for example, there may be a posterior displacement of the distal radial epiphysis; in the teenager the clavicle might fracture; in the young adult the scaphoid is commonly fractured; and in the elderly the distal end of the radius is fractured about 1 in. (2.5 cm) proximal to the wrist joint (Colles’ fracture).