Introduction

The wrist and fingers play a crucial role in hand function, allowing for precise movements, gripping, and manipulation of objects. The wrist acts as a flexible bridge between the forearm and hand, while the fingers provide dexterity and strength. These structures are composed of multiple bones, joints, ligaments, and muscles, working together to enable fine and gross motor skills.


Sections of the Hand

The hand can be divided into three main sections:

  1. Wrist (Carpus): Consists of eight small bones arranged in two rows.
  2. Palm (Metacarpus): Includes five metacarpal bones that connect the wrist to the fingers.
  3. Fingers (Phalanges): Each finger consists of three phalanges (proximal, middle, and distal), except for the thumb, which has two.

Skeleton of the Hand

The skeletal structure of the hand provides support and mobility.

Bones of the Wrist (Carpal Bones)

The eight carpal bones are arranged in two rows:

  • Proximal row (articulates with the forearm):
    • Scaphoid
    • Lunate
    • Triquetrum
    • Pisiform
  • Distal row (articulates with the metacarpals):
    • Trapezium
    • Trapezoid
    • Capitate
    • Hamate

Bones of the Palm (Metacarpal Bones)

  • Five metacarpal bones form the framework of the palm.
  • Each metacarpal is numbered from 1 to 5, starting from the thumb.

Bones of the Fingers (Phalanges)

  • Each finger (except the thumb) has three phalanges:
    • Proximal phalanx
    • Middle phalanx
    • Distal phalanx
  • The thumb has only two phalanges (proximal and distal).

Joints of the Hand and Wrist

The joints of the wrist and hand facilitate complex movements.

Radiocarpal Joint (Wrist Joint)

  • Type: Condyloid synovial joint.
  • Articulates between: The radius and the proximal row of carpal bones.
  • Function: Allows flexion, extension, and deviation movements.

Movements of the Wrist and Muscles Involved

  1. Flexion (bending the wrist forward)
    • Muscles: Flexor carpi radialis, flexor carpi ulnaris, palmaris longus.
  2. Extension (bending the wrist backward)
    • Muscles: Extensor carpi radialis longus, extensor carpi radialis brevis, extensor carpi ulnaris.
  3. Radial Deviation (Abduction) (moving the wrist towards the thumb side)
    • Muscles: Flexor carpi radialis, extensor carpi radialis longus.
  4. Ulnar Deviation (Adduction) (moving the wrist towards the little finger side)
    • Muscles: Flexor carpi ulnaris, extensor carpi ulnaris.
  5. Circumduction (circular motion of the wrist)
    • Combination of the above movements.

Midcarpal Joints

  • Type: Plane synovial joints.
  • Function: Allows slight gliding motions between the carpal bones, enhancing wrist mobility.

Carpometacarpal Joints (CMC Joints)

  • Type: Plane synovial joints (except for the thumb joint).
  • Function: Allow small gliding movements between the distal row of carpal bones and the metacarpals.

Carpometacarpal Joint of the Thumb

  • Type: Saddle joint.
  • Function: Allows flexion, extension, abduction, adduction, opposition, and circumduction, providing the thumb with a high degree of mobility.

Joints of the Fingers

Finger joints provide dexterity and grip strength.

Metacarpophalangeal Joints (MCP)

  • Type: Condyloid synovial joints.
  • Function: Allow flexion, extension, abduction, adduction, and circumduction.

Movements of the MCP Joints

  1. Flexion
    • Muscles: Flexor digitorum superficialis, flexor digitorum profundus.
  2. Extension
    • Muscles: Extensor digitorum, extensor indicis, extensor digiti minimi.

Interphalangeal Joints (IP Joints)

  • Proximal Interphalangeal (PIP) Joints: Between proximal and middle phalanges.
  • Distal Interphalangeal (DIP) Joints: Between middle and distal phalanges.

Movements of the IP Joints

  1. Flexion
    • Muscles: Flexor digitorum profundus (DIP), flexor digitorum superficialis (PIP).
  2. Extension
    • Muscles: Extensor digitorum, extensor indicis, extensor digiti minimi.

Conclusion

The wrist and fingers are complex structures that allow for a wide range of movements, from powerful grips to delicate precision tasks. Their intricate skeletal framework, joints, and muscles work together to enable daily activities and specialized functions in sports, work, and rehabilitation. Understanding the anatomy and biomechanics of the wrist and fingers is essential for optimizing performance and preventing injuries.