Flexion, extension, adduction and abduction occur at the wrist. The wrist is the joint between the forearm bones and the hand. It comprised of the radiocarpal and ulnocarpal joints, only the former of which is a true bony joint. The ulnocarpal joint is really an articulation between the ulna and the triangular pad of cartilage (TFCC).

The wrist joint is composed of two separate joints. the radiocarpal and the ulnocarpal. The radiocarpal joint forms between the radius and the cashew shaped scaphoid laterally and the croissant shaped lunate medially. The scapholunate ligaments link the two carpal bones. The radiocarpal ligaments support the joint on its radial side.

 

The ulnocarpal joint is a joint formed by the articulation of the ulna articulates with the TFCC (triangular fibrocartilaginous complex), which consists of the triangular cartilage (interposed between the ulnar surface and the triquetrum, with ulnocarpal and radiocarpal ligaments providing stability. The deep part of the pad of cartilage is called the ligamentum subcruentum, which attaches to the fovea on the head of the ulna. The superficial part attached to the ulnar styloid process. The TFCC acts to separate the carpus from the forearm, is the main connection between the distal radius and ulna, supports the proximal carpal row, and transmits the distal load on the carpus to the ulna. The sub-sheath of the extensor carpi ulnaris supports the joint on its dorsal medial side as does the ulnar collateral ligament. The ulnotriquetral and ulnolunate ligaments support the anterior surface of the wrist joint.

 

There is a proximal and distal carpal row of carpals, with the scaphoid linking them. The proximal row consists of the cashew shaped scaphoid. The scaphoid develops from two separate growth plates, and therefore has a narrow central segment. The lunate (moon) is so named, as it resembles a crescent, and articulates with the medial surface of the scaphoid. The triquetrum articulates with the TFCC, and the peas shaped pisiform sits on top of it (pisiform lies within the tendon of flexor carpi ulnaris). The pisiform does not form part of the wrist joint. The distal row is formed by the trapezium (with the first metacarpal); the trapezoid lies adjacent to the trapezium, and articulates with the second metacarpal. The capitate is the largest of the carpals, and articulates with the third metacarpal. The hamate articulates with the fourth and fifth metacarpals, and has a hook projecting from its anterior surface.

Flexion and extension of the wrist takes place at the midcarpal joint (between the proximal and distal carpal rows), with movement occurring at the wrist joint towards the end of the range of movement. Muscles in the anterior compartment of the forearm flex the wrist (flexor carpi ulnaris, flexor carpi radialis, flexor digitorum profundus and superficialis). Muscles of the posterior compartment of the forearm extend the wrist (extensor digitorum, extensor indicis, extensor carpi radialis longus and brevis etc.). Ulnar deviation of the wrist is caused by simultaneous contraction of flexor and extensor carpi ulnaris. Radial deviation is caused by simultaneous contraction of the flexor, extensor and carpi radialis.

 

There are two bursae that extend from the wrist into the hand, and surround the tendons of the long finger flexors. The ulnar bursa surrounds the flexor tendons of the little, ring, middle and index finger within the palm itself. The radial bursa surrounds the tendons of the flexor pollicis longus and extends to 2.5cm distal to the wrist joint.

Developmental precursor- Limb bud, somatic layer of lateral mesoderm

Blood supply- radial artery, ulnar artery, anterior interosseus artery, deep palmar arch

Nerve supply- Anterior and posterior interosseus nerves, deep and dorsal braches of the ulnar nerve.

Bursae- Ulnar bursa, radial bursa

Scaphoid is from the Greek skaphos which means boat

The wrist is the joint between the forearm bones and the hand. It comprised of the radiocarpal and ulnocarpal joints and allows flexion, extension, ulna deviation and radial deviation. 

Authors; S Shahid, A Davies