Anatomical Description of the Wrist

The wrist is a complex joint that connects the forearm to the hand, allowing for a wide range of motion. It is composed of bones, ligaments, tendons, nerves, and blood vessels. The structure of the wrist allows for a wide range of movements, including flexion, extension, adduction, and abduction. However, the wrist can be prone to injury and conditions such as carpal tunnel syndrome, wrist fractures, and tendonitis.

Bones: The wrist, or carpal region, contains eight small bones arranged in two rows:

  1. Proximal row (closer to the forearm): Scaphoid, lunate, triquetrum, and pisiform.
  2. Distal row (closer to the fingers): Trapezium, trapezoid, capitate, and hamate.

These carpal bones articulate with the radius (and indirectly with the ulna via a fibrocartilaginous disk) proximally, and with the five metacarpal bones of the hand distally.

Muscles: The muscles involved in wrist movement are located in the forearm and can be divided into two groups based on their functions:

  1. Flexors (on the palmar side of the forearm): flexor carpi radialis, flexor carpi ulnaris, and palmaris longus.
  2. Extensors (on the dorsal side of the forearm): extensor carpi radialis longus, extensor carpi radialis brevis, and extensor carpi ulnaris.

Ligaments: Numerous ligaments stabilize the wrist joint:

  1. Dorsal radiocarpal ligament: Stabilizes the wrist on the dorsal side.
  2. Palmar radiocarpal ligaments (radioscaphocapitate and radiolunotriquetral): Stabilize the wrist on the palmar side.
  3. Ulnocarpal ligaments: Connect the ulna to the carpal bones.

Tendons: Tendons are fibrous tissues that connect muscles to bones, allowing for movement. The tendons of the forearm muscles pass through the wrist and attach at various points on the hand and fingers. These tendons allow for a wide range of movements, including flexion, extension, abduction, and adduction of the wrist, as well as movements of the fingers and thumb.

Nerves: The main nerves in the wrist are the median, ulnar, and radial nerves, which are branches of the brachial plexus. These nerves control the muscles of the hand and provide sensation to the skin.

Blood Supply: The main blood supply to the wrist comes from the radial and ulnar arteries, which are branches of the brachial artery.

Fascial Compartments: The forearm, which houses muscles contributing to wrist movement, is divided into anterior and posterior compartments by the interosseous membrane and the lateral and medial intermuscular septa.

Joint Anatomy: The wrist is essentially composed of two joint areas:

  1. Radiocarpal joint: The primary wrist joint, where the radius articulates with the scaphoid, lunate, and triquetrum. This joint allows for flexion, extension, adduction (ulnar deviation), and abduction (radial deviation).
  2. Midcarpal joint: The articulation between the two rows of carpal bones. This joint also contributes to the four movements of the wrist.

Kinesiology: The movements of the wrist include:

  1. Flexion and extension: Bending the wrist forward (flexion) and backward (extension).
  2. Radial deviation (abduction) and ulnar deviation (adduction): Movement of the hand towards the thumb (radial deviation) and towards the little finger (ulnar deviation).

The flexor and extensor muscles of the forearm are primarily responsible for these movements, while other muscles contribute depending on the position of the forearm (whether pronated or supinated).

Understanding the anatomy and kinesiology of the wrist is crucial for fields such as orthopedics and physiotherapy, for the diagnosis and treatment of wrist pathologies, and in preventing injuries.